Car Engine Warmup Time

Bike friends of mine generally say 10 min but check with the car manufacturer because some now say to not sit at idle at all but to start driving straight away. I would guess though you should drive for about 10 min sensibly before thrashing the engine.

Just drive normally 'till it's warm.

Your temperature range is not extreme...

Just drive it!

While we are talking about cars....

When I check my tyre pressure ...they always seem to have gone down...but never up!

Am I doing something wrong? Maybe I should fill them with a gas that has larger molecules?

(worried of Harlow.....please only discuss this if you realise it is a joke)

Arrrr, you've got cold air in tyre syndrome, you need to drain all the air out and refill with warm air!

Alternatively.........

http://www.halfbakery.com/idea/Tire_20Pumping_20Hubcaps#1080320400

that'll be why they put water in traaaactor tyres, then, jethro.

because I expect water is a bigger molecule than air.

one question: is your tyre only flat on the low side ? if so that is a pretty good indicator that you are in the northern hemisphere. if the upper side goes flat first then you are in the southern hemisphere.

it gets to be a bit of a b*gger on the equator, though... and that explains why there isn't much intensive agriculture in West Africa or the Amazon.

because I expect water is a bigger molecule than air

I'm pretty sure you are right. The natural water molecule size is the size of a rain drop. Fog is an unnatural state with too-small particles -- that's why it's hard to drive in fog. However, if you watch fog on your windshield, you see the tiny unnatural particles combine into bigger ones the are JUST ABOUT THE SAME SIZE A RAINDROPS! That can't be coincidence.

So if you fill the tires with water, it can't possible leak out, unless you have holes larger than the size of a raindrop.

that's why it's hard to drive in fog.

So when the car manufacturers test cars in a wind tunnel, for drag coefficients they should, more realistically test in a fog tunnel, because the drag that fog has on a car is greater than the drag that dry air has on a car... ? I always wondered why I travelled more slowly when it was foggy. Now I know. Thanks for this.

And instead of quoting mileage in Urban, Highway etc., we should be quoting Urban Desert, Urban Tropical Rainforest, ....

Good suggestion re testing in fog tunnels. Studies have shown that fog can work its way under the accelerator pedal, making it harder to push down -- this also causes people to go slower in fog.

When I was young, we mistakenly thought we should go slow in fog because we can't see. Now, we understand that such behaviour is selfish -- there are plenty of people behind us who need to get to where they are going on time, rather than spending all day stuck behind some safety nut.

Del,

I got tyred (pun intended) of that same problem, so I soldered little funnels onto the valve stems of my car that face forward with normal rotation. Now it fills the tires as I drive, and the faster I go, the stiffer the tires get (this is really a performance enhancing trick). Backing up is a real b1tch though...

Problem solved!

Reminds me of the blonde joke I heard recently. She was happy the service station attendant was so honest when she took her car into the shop. Seemed she only needed turn signal fluid.

Hi Del

"When I check my tyre pressure ...they always seem to have gone down...but never up"!

This is generally true, but I moved to Arizona for a few years and found that after a 65 MPH drive, across the desert, in the summer my tire pressure would rise by 5+ psi even after only one hour driving.

Here in Sacrmento they always go down -- even my brand new "Tiger Paws"

Rich

You must have very good locking lug nuts...and perhaps you're new to Sac'to(?)--also known as Baghdad of the West--with its 40 (x10³) thieves (not counting the municipal court). Here, if they can't steal the tires they get the next closest thing: the air in the tires. (Doesn't seem to really matter that the air is not worth much; its the thrill of the steal that counts.) Since my vehicle is kept locked in my garage, the tires (regular Generals about 6 years old now) always need air only at winter's start; deflating only when the weather goes into drought mode around May.

Checking the stem cores every so often, keeping caps on, and watching tire installation to make sure they don't skip greasing the rims probably doesn't hurt either.

DNA and RNA are two commonly used molecules for fixing this problem with tires. Unfortunately, using such molecules is just a work-around.

The real problem is that the tires have tiny pinhole leaks all over the place. These are microscopic, so finding an individual leak is extremely difficult. On my own tires, I have inserted upwards of 1000 pins per tire in random patterns so that those pins fill up the micro-pinholes, stopping most or all of the leaks. When you do this you will find you will have urges to put a pin in a particular place -- it's as if your brain is trying to say: "I KNOW there is a little hole there." Don't get caught! Be sure your placement is completely random, because the little holes are completely random in their placement. If your pin placement is also completely random, then you should plug every one. Good luck.

Hi Ken, I need your advice. I tried your method above but there's a few problems. Firstly I couldn't get the pins into the tyres. I thought I'd solved this one by using a pneumatic nail gun but all I've ended up with is a bunch of flat tyres. I think the problem may lie in the randomness of the placement. No matter how I tried, I kept finding myself making patterns. How did you manage to keep the placement completely random and do you reckon I'll be able to retro-randomise these nail studed tyres before I've got to take the car back to it's owner?

One other thing, I don't know if it's relevant or not, it seemed like the later nails I put in didn't seem to have as much effect as the earlier ones. Do you reckon this means I was getting the hang of the random bit? Perhaps I should borrow another car now I've honed my random skills?

It sounds to me like you are getting the knack. I'm sure you've already experienced the problem in which you think to yourself "I think I'll put one.... there!" and just after the thought develops you realize you've thought too much, destroying randomness. So when you have such thoughts, of course you should place the pin (or nail) elsewhere. The ideal situation, the skill for which you will develop soon, is to develop a reflexive full body twitch combined with a trigger squeeze.

I wouldn't worry about trying to retro-randomize. Just deliver the car with flat tires, and explain what you tried to accomplish. The owner will appreciate your efforts, and will probably say something like "Gosh, golly, thanks, it's the thought that counts." I went through four or five friends' cars before getting the technique right. So press on -- there is nothing like the satisfaction of being drive away from a filling station while others wait in line to use the air hose.

Thanks Ken. Unfortunately I may have to pause in this quest. I returned my first car to it's owner and he proposed an alternative project.

On the face of it what he is suggesting I do with my nail gun seems anatomically impossible and extremely uncomfortable, if it was possible. However he was very (very!) insistent so perhaps the suggestion has some merit. In the mean while I intend to practise my randomness at every opportunty. As soon as I find myself thinking anything I intend to think of something else. I'll keep you posted.

I've been practicing that random thought pattern for years -- and it

what was I gonna say?

Well Ken, all I can say is it's a sad world. As soon as you come up with a good idea everyone around you tries to steal it and others work to suppress it. Having received medical advice to abandon the alternative project suggested to me I decided to revisit your no leak tyre idea. I'd been practising the RBT (reflexive body twitch) in front of the mirror till I was certain that I had it right. Then I went out to borrow another car...... no way! I couldn't believe it; all my friends refused. I can only conclude that word of your method has got around and they wish to beat us into commercial production. Don't they understand that I only do this for the good of mankind?!

Anyway, I had a brilliant idea. Off to the local service station where I connected my nail gun to the air line and got busy on any tyre I saw. Now I don't know if you encountered this problem but with truly random nailing you don't always hit the tyre. I've found aiming spoils the RBT. I also found the length of the airline limited true randomness. I'd recommend an airless nail gun.

Great success though. My actions attracted a lot of interest and whilst some of the comments were a bit negative I put that down to jealousy. I also had the satisfaction, as you said I would, of driving (well, being driven) away from the service station and looking back at a line of cars, and an ambulance, at the airline. Wonderful!

I have encountered a problem though. My experiment this afternoon was so succesfull that I've attracted unwanted attention. I'm sorry as I know you intended to keep this low key but I think vested interests in the rubber industry are out to suppress this invention. How else can I explain why they've kept me locked up all afternoon. They keep telling me that none of my friends will go bail but I know they're really being paid to keep me out of circulation. I've been allowed to post this messsage as they're very interested to contact you. Is acccessory before the fact some sort of term meaning we get to share profits from this. I know it's really your invention but I feel that I've made some important developments to the concept.

One other thing, I don't know if it's relevant or not, it seemed like the later nails I put in didn't seem to have as much effect as the earlier ones. Do you reckon this means I was getting the hang of the random bit?

Depends on the nails. If the fog is making them rusty, try using galvanised ones instead.

When I check my tyre pressure ...they always seem to have gone down...but never up!

Am I doing something wrong? Maybe I should fill them with a gas that has larger molecules?

A LITRE OR TWO OF RUBBER PAPER GLUE FROM THE STATIONERS PER TYRE WILL STEM THE FLOW!

depending on how new your car is......carbureted engines required a longer warm up time. fuel infection whether throttle body or port inj only need about 30 seconds in warm weather and about a min in cold, mainly to give the oil time to circulate throughout the engine.

For normal use, i.e. the car is used everyday, you can and should drive off as soon as the engine is started, albeit taking it easy for the first few miles...

If you have a car like mine, which has only done 12,000 miles in 14 years (honestly its true!!!) and the last time I used it was 8 months ago (no it IS true!!!). Then I don't know but the oil must have drained away and the engine rusted up, for all I know, so I always start the engine and leave it for 30 minutes to warm up gently the day before I need to use it....

Ohhhh I also drive it around a local industrial estate for 30 minutes as well with the brakes hard on to clean off the rust on the disks!!!!!!!

Don't know why I don't just sell it and hire a car when needed?!!

John.

Geez, John, just how DO you give brakes a hard on?

Hank

HI Electroman,

You should probably use the hand crank and turn it through a few revs to get the parts somewhat coated with oil (it did come with a crank didn't it?). Then start it and warm it gently.

What kind of car is it if I might ask? Just curious. I had a 1971 Triumph Stag for quite a few years. I probably put no more that 30 miles per year on it. I finally sold it because parts got too hard to find as well as too expensive. I really babied that one; warmed it up slow and drove it easy.

-John

I had a friend about 1975 who drove a TR Stag, he drove up north in the UK one very rainy evening and the car got slower and slower, he really knew that he had a problem, but he did not want to stop and get soaked. In the end he was being overtaken on hills by trucks and people on bikes.....

When he got to his destination, he opened the boot( Trunk for US Citizens) and found it completely full of water! And it was a big boot, he probably had more than a Ton of water in there.....

He sold the car once it was dry again!!

He should have kept it! The only Stag that has water in it...........

Hi PibMak,

You're dead right there. Stags were known for their overheating problems

Part of the problem was that the water pumps were too small. (design problem). Been a long time but seems like I recall resetting the clearance between the impeller and the housing. Seems the factory setting was a little on the loose side. Also, different head bolts/studs were installed to prevent those aluminum heads from warping. After that I never had cooling system problems with it.

However- that Lucas electrical system... *&%$##%*...

-John

Wasn't the Stag also one of the last cars with a "Mechanical" fuel injection system that gave people nightmares?

Hi Andy,

I'm not sure about 72 thru 75 models but my 71 had dual Weber sidedraft carbs. The V8 engine was, essentially, 2 Saab 99 4-cylinder engines joined together (not literally, but from a design analogy...)

Regards,

-John

I understood the biggest problem was the drive on the water pump, made of a low spec steel that, as it resided in the coolant, rusted through pretty quickly.

Ah, the Lucas electrical looms! I have a few stories about my old 1967 Triumph Herald Convertible!! I had to scrap it in the rain on the Hoggs Back ( old Southampton to London road) at 2 in the morning! I think I got a short after the wipers stopped removing the normal molecular sized rain drops and flames started to lick out from beneath the brush walnut dash! the rain finally put out the fire but there was not alot left of my beloved Betsy! I still miss her!

I´ve also heard of another interesting tyre remedy which includes in my opinion rather alot of screws! I think it is a slight improvement on the NGM (nail gun method) due to the fact that there is more of a grip on the rubber, I fear that in v.hot countries the quantity of nails in the tyres would in fact increase the temperature dramatically thus, firing the nails out of the tyre! The NGM is fast but I think restrictive! Due to my hectic work schedule, I fear, I cannot do any exhaustive tests! If anybody is willing to investigate this further, I would love to hear the results.

Your tire sealing method has a lot of merit. A lot of screws almost has to be a good thing, with tires or not.

No hand crank.... I think the last one I saw was back in the early 60s...

I could try putting it in gear and pushing it round the block for half and hour I guess...

Maybe the automatic transmission would need a big spanner dropped in side it to 'mesh' the gears???

I normally warm it gently by building a bonfire under the sump and set light to it.... after a while when I can here burning rubber and hydraulic oil I try the starter...

John.

When young, I used to idle my motorcycle(Triumph T110) for about 15 mins- I was always reboring & rebuilding the engine because of excessive wear- I asked an older mechanic- he said " I just start the engine at a brisk idle, & immediately back down my drive, then drive moderately until engine warm"- I have followed this advice all my motoring life, & never had any trouble. I once worked with a bloke who started his car at full throttle, running up to full revs- you should have heard the knocks in that engine!. As to tyres, mine are only flat at the bottom- as to gas, try Nitrogen instead of air for less temperature difference/ pressure/ hot/ cold.

you should wait till the temp guage moves once it moves

you can drive off safely but do not rev hard

until it reaches full operating temp

then have fun

This would involve me starting my car about 30 minutes before I want to leave (based on the fact that it takes at least 5 miles of reasonable driving for the thermostat to open to the point where I can get warm air on my toes!)

<mutter: and then it's only on my toes if the clutch is fully depressed, since the air vents weren't positioned to put air on your feet in a normal driving position. Grrr>

A footwarmer might be of some use?

And I could fill it with ice during the long hot summers!

Cold feet. Now there's a thing....

If you had a foot warmer like that you wouldn't need it! You would just say 'Carruthers, warm up the Rolls and bring it to the front, would you!'

Well, I am a car nut! and the manufacturers say just start it and drive. But I think form a material property stand point, you need to allow the fluids and metal components time to adjust from the cold temperature transittion to warm. As well as when you start the car up when its warm to allow fluids to move/cycle their way through out the engine/transmission. Now it you have a mechanical oil pressure gauge you will notice that maxium oil pressure is not acheived until the car has run for about 30 to 60 sec. That tell you right there that the oil has not reach its full lubrication protential. Think about what happens when you shut a car off all fluids drain back to a pan. when you start the car up the individual pumps start to cycle and move fluid, its really not instantaneously. I prefer to let my car run for ten minutes at low temperatures and 2 to 3 minutes at warmer temps.

Bri

I think we're all nuts in this thread....

I just start the engine, put the seat belt on, nudge the car into the drive, close the garage door and go gently until the temp gauge is up to norbal.

On the motorcycle I wait a touch longer 'cause it has a propensity to stall if it's not a little warm.

On the bicycle it's the lard on the seat that has to get warm. Wish I still lived close enough to the office to take the bike....

As far as tire inflation, I just throw in whatever the compressor is delivering. But I check it a lot. The tire pressure, that is. I do have water and calcium chloride in the Farmall. Nothing worse than turning a tricycle gear tractor turtle. And those suckers never go flat!

Except for extreme cold weather, the critical parameter is not engine temperature but oil pressure. Even extreme cold is really just a parameter that keeps the oil from flowing freely until the engine is warm. Oil is more viscous at lower temperatures and thus harder to pump.

Oil must be fee flowing through all engine contact parts before acceleration or load is placed on the engine. Otherwise excessive wear will result in those parts that don't have a sufficient film of oil on their surface. (Main bearings and rod bearings are typically the last places to get oil in the startup process)

I use the 60 second rule to get oil fully pumping through the system and flowing back to the sump at idle before applying load. (Think of it like filling a long garden hose with water… it doesn't come out the end of the hose when you turn on the faucet.) Take longer during extreme cold weather.

Agree entirely about the oil viscosity.... AGMA ratings and all that.

EXCEPT Toyota engine blocks. I have seen several old Land Cruisers lose hoses and the engines seize up - one of the most memorable times was in Wadi Rhum ( the Mountains of the Moon ) in Jordan. The temperature was 130F + and a hose burst. The engine seized almost immediately. The owner shrugged and said he would come back with a new hoze and water the next day, so we abandoned that truck. Next day sure enough, replaced hose. Added water. Started and ran.

I also did the same thing with a Toyota Corolla in the UAE - on the way to the airport - actually ran out of water !!!! (Pool car !!) . Stopped the engine for 20 minutes. Added water. Still made the flight.

Question: what is different about Toyota engine block metallurgy. I'm not sure that you can do this with every engine, can you ?

We have lost all coolant on a tuned Ford Pinto engine at least twice, ran the engine till it stopped, let it cool down, refill, and it's still going. This is a track day car that gets severely hammered.

(See above)

Just proves the Dead Ringers' "Life on Mars" assertion that it's still 1973 in Norwich!

Bodie - cover me!

Shut it!

Leave it out, George.

Stop SHOUTING!

I dropped all water and oil out of my R-reg Astra - got a tow, head skim, new belts and she ran fine for another couple of years...

Re the Toyota: check out the Top Gear report on the one they tried to kill - even after leaving it in the sea over night, it started up after fluid flush and refill! It still started after they droppped it off a cliff too.

Similar story with an L-reg one. The head-skim, not the seawater and the cliff, mind you. Is there any truth in the rumour that an Astra will dissolve in seawater leaving no solid residue?

I came back from a long heavy drive up the motorway and noticed that there was a spot or two of oil where I parked...

I looked under the bonnet and found the oil filter had popped off!!!

As I had been driving at over 80 on the M1 I doubt if it could have been running with no oil very long, but I will never know I guess....

John.

I assume you had no warning on the dash? No idiot light or anything?

I very good friend of mine has an Impreza that ran out a big end on Christmas eve last year. We did think about rebuilding it, but as he had driven it home for 10 miles, and the cost of a gasket set coming in at around £700, a second hand engine was acquired. (For about £400) Last Saturday I stripped the old engine down. All the big end bearings were down the the backing metal, except no 4 which was gone. (I.e. not there) The mains had picked up the loose material from the disintegrated bearing, but apart from that looked ok. The crank - Beautiful, a work of art - and no good to man nor beast.

The point is, the ecu would not allow the car to be driven until it was warm, the car was serviced regularly with the correct oil, and was not badly mistreated - i.e. only thrashed a bit. The coolant was maintained at the correct ratio and not allowed to run low, and the car had only done 60,000 miles. (My Honda has done 160,000 miles and has been roundly abused from cold on wards.)

So go figure.

only thrashed a bit:

Surely they use tractors these days to plough the fertile field of Norfolk instead?

Huh! I do that in the Capri! Have you been to Snetterton lately?

In reply to 17 & 19- re ice seizing & being used again once cooled & fresh coolant added- this is definitely against the present day norm- one could ask why- most likely is that, when an ice seizes due to overtemp, due to loss of coolant, it is the pistons that lock in the bores- if just so clearances, as in most domestic cars, it is goodbye motor!. However, in the case of well used motors & racing motors, the piston to bore clearances are greater, so once cooled, could be freed, though as has been said, with greatly increased noise/ oil consumption/petrol consumption/ power loss.(& diesel consumption, if so fuelled). To prevent this catastrophic event from occurring, I have long used a low coolant alarm, & also a cylinder temp over heat alarm- these are cheaply & easily made if you have electronic knowledge( the low alarm is a voltage comparator, the overheat is a bimetallic switch, both sounding piezzo alarms in cab if triggered). They also have test functions so you can test all sound at any time.

Just start it up and drive it sensibly, got 300,000 plus miles on my 85 Chev and been driveing it 15 years just like that every day. Never had to touch the internals on it in all that time. Post 15 , nope, rod and main bearings are the first place that gets oil, rockers are the last. J

I believe your explanation is best. Years back, it was recommended to wait a few minutes and 10 was not the answer. Even today, in cold weather I wait until the temp gauge needle comes off the peg, but only a minute when ambient temp is warm.

One thing to keep in mind is, if your car is fitted with a CAT (catalytic converter) the rich fuel mixture at idle will shorten the CAT's life

The recommendations that I follow is, use the right grade of oil for your climate. And unless it is super cold, idle your engine for 30seconds or so before driving it, this apparently is enough time to circulate oil through out the engine. An auto mechanic told me this. He also said excessive periods of idle time will actually increase carbon deposits in the cylinders and spark plugs.

Although, when I used to live in the mountains where it snowed daily in the winter, I would go outside and start my jeep in the morning, then take my shower and breakfast about 20minutes later the engine was warm enough to run the heater.

Electron Oasis and ca1ic0cat got it right, the rest is either partially or completely incorrect.

Provided you have the correct oil for the engine and environment, the oil reaches all parts of the engine within about a second or even less, provided the engine has not been left for months without turning.

If the engine has not run for a long time, then remove power to the ignition system or just pull off the plug leads (diesels are harder in this respect!) and crank the engine for about 10 seconds, not more as you will pump petrol into the cat and damage it. Connect up the ignition and start the engine. Do not over rev.

If the engine is used regularly, then just start, take the time to put on your seat belt, then drive away without overloading the engine, with only reasonable revs, not racing.

Driving warms up the engine and the cat the quickest, but wait until the engine is properly warm before flooring the gas pedal !!

Although an engine may run after seizing and cooling down, a look at the piston and cylinder walls will show significant wear that will result in blow-by and higher oil usage than necessary....

Using the best oil and the engine manufacturers oil filters will give the best results.

The way some people in the USA use cheap oil and frequent oil changes does not actually result in a long-life engine sadly, it just places more used oil into the environment!

Using for example modern Longlife III Synthetic oils allows for long distances between changes (30,000 Kms are normal) and reduces the wear on the engine, thereby increasing its life and significantly reducing the amounts of used oil into the environment.

If you do not understand the major differences between synthetic and normal oil, check the internet, but the differences are like chalk & cheese!!

If the engine is used regularly, then just start, take the time to put on your seat belt, then drive away without overloading the engine, with only reasonable revs, not racing.

You drive a petrol car...I know this because most diesel drivers use the glow plug "on" time to put on their seatbelts - especially in winter!

With the Doble, one could probably do the breakfast washing up and shine a couple of pairs of shoes as well.

There's a good example of a Doble in the Ford Museum in Detroit, Michigan, USA.

With most modern diesels, especially with VW Pumpduse or Common Rail engines, you can start immediately, just like a Petrol engine.

My Mitsubishi Grandis with a 2 liter VW TD-I motor starts immediately at least down to -18°C (It has not been colder than that since I had the car......)

Diesel cold starting is more a function of the size of the fuel drops(the pressure in the fuel lines) and the compression ratio. That is the smaller the drops and the higher the compression, the easier it is to start.......

Glow plugs are rarely needed for starting, but still installed, they probably let the engine run more smoothly in the first few seconds after starting......

I think it depends on the type of diesel you have. Indirect injection offers some advantages in naturally aspirated engines but requires glow plugs. Direct injection does not require preheating and is easier to turbocharge, hence the swing away from glow plugs.

Regarding the warming of engines, warm it as quick as you can without hurting it; ie drive off as soon as you have oil pressure but don't push it until the temperature gauge comes to life. If your vehicle of choice happens to be a piece of heavy machinery that doesn't do anything but work hard you may have to grin and bear the extra wear whilst it idles itself warm, rather than risk major damage.

Indirect injected engines are less efficient, which is the main reason they are going out of fashion. Fuel economy being the great driver, as well as power per liter of engine capacity of course....

As far as I am aware, there are no cars WITHOUT glow plugs, even if not needed for 90% of the time here in central europe! As the other 10% could be very annoying if the engine does not start!!

Sorry, careless typing on my part. My "no glow plugs" should have been "no 30 seconds every time you start".

I'm not so sure though that indirect injection engines are less efficient, although I claim no special expertise on automotive diesels. Before turbos became common there were heaps of IDI diesels around. Why would they have bothered if they were harder to start and less efficient?

AHA, you have to remember old diesels first which were direct injection, but very, very noisy, then you understand why indirect diesels became popular because they quietened the everthing down, but were inefficient! The port that was used to get the burnt gases to the piston slowed everything down a lot and allowed the gas to cool e.g. reduced efficiency.

They make modern direct diesels quieter in a number of ways technically, but basically its the same method, they inject the fuel in small amounts over specific arc of engine movement, so instead of one big bang, you get lots of little ones, so to say....

It also allows you to make the engine a tad lighter with more aluminium parts, the stresses are significantly less. You also get better fuel economy as an important side show!

Direct injection is used in a number of petrol engines to as a way of improving efficiency & economy, but has proved quite difficult to achieve properly for some companies....

I have simplified this a it, but I am sure that you get the idea....

"How long should I run the car engine in idle before driving? Climate in my place is generally warm (Summer temperatures 20 to 35 deg C and winter temperatures 0 to 20 deg C)."

A half minute or so should be adequate to get the oil circulating and thoroughly lubricate all moving surfaces and bearings. Once on the road take your time till the engine temperature stabilizes before trying to be a Dale Earnhart wannabe.

Watch the 'temp.` gauge. - When it starts to move the thermostat
has opened and the coolant is in the operating range.

My car manual tells me to start the car and move, as idling the engine without moving the car would damage the Catalytic converters. I have done this with all my different cars over the years, without any problem with the engines. Of course I have always used Full Synthetic oils, changing oil and filter at 25000 miles, or once a year, not every three months as almost everybody does. It is a fact that lot of car owners use cheap oil and pay more in the loing run by using more oil and even ruining the engines on their cars.

You are 100% correct in all you say. I agree completely.

Over the last 22 years or so I have had several cars (diesel & Petrol) go to between 250,000 and 370,000 Kilometers before being sold in a running condition.....the engines were still top notch. They started and ran like new AND none of them used much oil, that is less than 1/8 liter per 1000 Km.....some just got down to the minimum between services......that is 1/2 liter in 10,000 Km.....on one.

I have had 4 x VW TDI engines too, after initial run in, they hardly used any oil at all. They all were sold with around 120,000 Km.....

I have had a lot of cars!!! and driven between 50,000 and 80,000 Km per year myself, plus what the wife and Kids drive.....

Always the best oil that money could buy, changed on the dot or fractionally before if I had a long journey coming up, and the original filter from the car manufacturer, no look alikes!

First, let's assume you're referring to car models within the last approx. 50 years--since universal fitting of engines with automatic chokes. The more appropriate question, then, would be: How short...should you idle...? And the answer: as short as possible.

Although it might seem counterintuitive, idling an engine actually increases the time needed to bring it within "normal" (i.e., acceptable) operating temperature range. To warm the engine to the same degree, say, as just 1 - 3 minutes (a mile or so) of driving can take as many as 15-30 minutes, or more, at idle--as anyone warming an engine at idle for maintenance purposes well knows. (But good maintenance techs should also know better than warming an engine at "curb idle.")

Before thinking about how long (not) to idle after cool and (especially) cold starts, one must consider why it is, that idling too long is detrimental--how it will wear out (even damage) the engine more quickly--as others have stated.

With cold starts, the fuel charge (entering the cylinders) is enriched as a result of choking (or its computer controlled equivalent), and continues that way until choke unload/kickdown--this can be accomplished "pedally" (stomping the gas pedal) with older, (typically) normally-aspirated engines (however the gas pedal should never be "touched" in association with engine start-up on computer controlled, fuel-injected engines); or automatically with both older and newer, carb-equipped and fuel-injected engines. Aside from choking, newer, computer-controlled car engines also received enhanced fuel enrichment (by computer command, and at all ambient temperatures) at start-up idle (just the same as happens at wide open throttle (WOT) operation, or during AC cycling) in order to keep the engine from stumbling or stalling. During these periods of excess-fuel enrichment the rings and cylinders are washed with higher than normal amounts of fuel (of oil solvent), the consequence of which is that the oil lubricating the cylinder walls is partially dissolved (and thinned) by the excess fuel. This effect is cumulative over time, with the result that excessive warm-up idling can result in prolonging of insufficient lubrication of rings and cylinder walls, and in consequential, accumulating damage.

For this reason, it is imperative to bring the engine to normal operating temperature in as short a time as possible; and the only way to do that is to operate the engine under moderate load (no hard acceleration; speedometer at 50 or less) as quickly as practicable after engine start. Said another way: it is better to run the engine under enriched-fuel-mix (i.e., curb idle) conditions for a matter of seconds, than it would be for a matter of minutes x5, as would be required to warm the engine to the enrichment-cut-off engine temp by no-load idling.

How soon after engine start, then, should the engine be operated under load, without it being too soon? Apart from not wanting to idle any more than absolutely necessary, there is no "hard and fast" rule, since idle-before-operate time will vary based on such factors as ambient (hence, engine and engine oil) temperature...and how long since the engine was last operated. The owner's manual for your car model, or just about any other car model, should provide some basic guidance. Generally, idle time should be just long enough to allow oil to be pumped to the top of the engine where it can lubricate critical moving components (tappets, OHC, and lifters) in addition to rings and cylinders; also, long enough to "pump up" hydraulic lifters in vehicles so equipped. In warm climes, or where the engine has run recently, this can be a matter of seconds; in moderately frigid weather...perhaps 30 seconds to a minute or so. Another good practice is (with radio and accessories turned off) to listen carefully to the engine for "tells" that the engine is running smoothly and can be driven away under load. For example, after accumulating some mileage, some engines will be heard to issue forth tappet clicking on initial startup, clicking which stops (indicating that lubrication has reached engine top and lifters are pumped and seated) after a few seconds of idling. Listening to your engine under various start-up conditions...you will quickly get a feel for when it is ready for work after start-up. Hope this answers your question sufficiently.

Well said!

Andy, Ken:

Thanks for the kind words. Noticing Andy's avatarpics, here's something I thought you might find...amusing? The first is an almost eye-level view of the stealth bomber just seconds (the time it took startled shooter to pan up and get a bead on it) after the looming, giant "bat" machine passed--almost silently (on glide path, no doubt)--within a few hundred feet directly over my house; and just seconds before the plane disappeared (about two miles away) into nothing more than an almost invisible thin line (something like this: ____) in the Calif. sky.

And here's how it looked after its air show flyaround on its way back to where it came from.

Sorry, images are not as clear as originals--definition evidently lost during upload.

Please forgive for my getting off topic.

Nice complete answer.

The handbook in all Volkswagens (usual disclaimer) advises one to just drive off immediately after starting.