Synthetic Oil vs. Real Oil

You do not state which Pennzoil? Mobil 1 is a fine oil, as are the Pennzoil oils.

As a general statement, Synthetic oils (they are real by the way) are "better".

However, an older engine, if it has not been using a synthetic oil from new, will probably be better off using a good quality conventional oil.

Note that Pennzoil makes synthetic as well as conventionaly refined oils.

Choose one and then use it only. Flush well before changing to another oil even of the same brand and even if the oil company tells you they are compatible do not mix any of them.

If the vehicle has run Mobil 1 all it's life, I'd continue to use it. It's more expensive, but the change interval is longer. And, it is better. Although you may never use the car long enough to know for sure.

If this is the dealer's opinion and he doesn't know the life history of the vehicle then I'd say it doesn't matter.

The car has always used synthetic oil. My machanic says synthetic oil does not clean the engine. Any truth to this?

Thanks to all for your thoughts

Really good post.

GA from me.

I would only recommend Long-life 3 Synthetic oil, its better than both 1 and 2.....

I have used this on my last 3 Diesel cars, all had the 140 BHP 2.0 TDI motor....

I used to use Synthetic on my cars 20 years ago, never had an engine get damaged on about 8 different cars with up to 400,000 KMs.....all were running normally when sold.

You can also extend the time the oil stays in the engine, I have a diesel and run it around 30,000 KMs, or just over 20,000 miles (conversion from my head).....

Its far far far better than any mineral oil......as Ed has already said.

Change your mechanic, he hasn't a clue, or he's hoping for more business using the wrong oil, either way, you got a dud mechanic.....

If the car has always used synthetic oil then do not change.

Synthetic motor oils (or their additives - see Ed W's post) do indeed keep the engine clean and do "clean" very well; in fact this is one of the problems with using them in an old engine that has used conventionally refined oils.

Your mechanic may have heard that synthetic oils have a lower "dirt carrying capacity" than conventional oils - this is true, but seeing that they produce less "dirt" and motor car engine oil is changed frequently this is neither here nor there.

Stay with the synthetic.

Find a new mechanic as he is so behind the times and his knowledge (or lack of it) is faulty! Mercedes recommends it and synthetic oils are so superior it isn't funny!

With the syn the MPG will fare better by 2-3 mpg and cost effective as engine will go longer too.

Is it your car, or the mechanic's car?

He should do as you instruct, not argue.

If the previous owner had no problems with the synthetic, use it.

They (synthetic oils) are much better than when they first came out.

I've heard the synthetic oils can go to 15K, even 25K miles between changes. What about the filter? Can the oil filter last that long, or does it need to be changed midway?

As you have heard early studies conducted 20-30 years ago showed that synthetic oils could effectively protect an engine for 15k-20k miles. It was not until the mid-nineties that ads from places like "Jiffy Lube" and auto parts dealers argued that synthetics could only protect an engine for 4k-6k miles.

I personally have always considered the earlier studies more credible largely because my father has been changing the full synthetic oil and OEM oil filter in his vehicles every 10k miles for at least 20 years now. To date, none of the 4 vehicles that he has maintained in this way have ever shown signs of major engine wear even after rolling over 150k miles (two of those vehicles were sold).

The simple answer to you question is yes, but for more detail here's a statement and a link from a group that claims to be completely independent that has been working on a long-term "real life study" since 2002:

Past Results

To date we have completed our tests of Mobil 1 and Amsoil. Mobil 1 held on for 18,000 miles, and didn't need its first oil filter until 12,000 miles. For all the details, visit our Mobil 1 Test Results page. Amsoil was time-limited to 14,000 miles (its year ran out), but it made it the whole way without a replacement filter. It's not a total success story, though, as it had some trouble with its viscosity. To read all about it, visit our Amsoil Test Results page.

http://neptune.spacebears.com/cars/stories/oil-life.html

I tried that link for the Mobil 1 test results and got a "you are so screwed" error 404 message that the page has moved.

That's funny. It appears that if the author's conclusion is not enough for you then you have to pay the $20 donation to view the actual data from the study; either that or the site is a scam... Hope my anti-virus is up to date.

There's a disclaimer link on the "screwed message page" that verifies that the site is profit driven:

http://neptune.spacebears.com/cave/index.html

There is a section titled "Blatant Plea for Help" elsewhere on the site that discusses the $20 donation to help with research costs.

http://neptune.spacebears.com/cars/stories/oil-life.html

(FYI - I have no intention of donating.)

Try this web site for a pretty comprehensive test of synthetic oils.

http://www.performanceoilnews.com/oils_against_oils.shtml

They appear to be unbiased and do a pretty good job of covering the spectrum of synthetic oils available on the market.

I've heard the synthetic oils can go to 15K, even 25K miles between changes. What about the filter? Can the oil filter last that long, or does it need to be changed midway?

These are acceptable synthetic service intervals when employing a bypass filter set; use two filters one 5-7 micron and follow with 2-3 micron.

For YOUR sake, do NOT switch! I have seen several engines ruined by switching to Penzoil from other brands.

I have also used Penzoil in several of my vehicles since new with great results.

It seems that when you switch and clean out a high milage engine with Penzoil you change the broken-in tolerances and bad things happen.

One engine belonged to my daughters boy friend who was driving his car 150 miles each way to college and after switching was experiencing a quart every 30 miles usage (the car never did smoke, old mechanic said the oil was leaking past the exaust valves thus never entering the combustion chamber). After switching to straight Valvoline and putting several hundred miles on the car, he was up to a quart every 1200 miles. The car lasted two morw years through his college days.

My advice is, stay with what the car is used to.

find a new mechanic now if this is what he recommends its for his bennefit not yours!!!!!!

In my general experience, as well as having had this exact same discussion several times over the years with two lifelong mechanic friends, three family friends who have been car dealers all their lives, and my wifes car needing to have the heads removed and the engine cleaned out because of this issue:

Quality conventional oil is good, does fine, and will keep your engine in good shape for the expected life of the car, as advertised, while the rest of the car rusts apart around it.

Synthetic oil is "better" based on several parameters, particularly the capability to operate safely at much higher temperatures down at the molecular level without breaking down into sludge.

IF your car had been using conventional-oil: you MAY go to synthetic blend or all the way to Full Synthetic. You would likely need to have them use a "motor flush" product, followed by the new synthetic blend or fully synthetic oil.

AFTER your car has used Synthetic, ALWAYS use synthetic.

Any mechanic who thinks he can simply drain out a fully synthetic oil from a car that has always had nothing else, and simply dump in a conventional oil that he likes...needs to have his toolbox checked for moonshine.

IF your Mechanic simply has a personal bias in favor of the Pennzoil brand, is a big Kevin Harvick fan, or has a nicer margin-commission from the sales of Pennzoil?

Then fine - use Pennzoil Platinum.

It is a perfectly acceptable substitute for Mobil 1, and the Pennzoil marketing says this: "Cleans out sludge better than our conventional and synthetic blend oils."

CASE CLOSED.

Westbye, You've gotten generally good advice here.

Now I will give you even better advice- Do yourself a favor and buy the owners manual for your car, look up the engine oil specification, and do what the manual recommends.

You see, the manual is written by the German automotive engineers who designed your car and engine. Obviously, their recommendation is better than that of your mechanic, this forum and even your dealer.

Rayzer

I've been told I should use a conventional oil for the first 1000 miles before switching to synthetic. Is this true?

Do you know how much Mobil 1 pays to get their oil listed as OE?

Not a clue. Just posted that in response to the previous question about break-in.

Do you?

No I don't, but there are many things that happen behind the scenes in guise of marketing. Hollywood films have used product placement incentives for decades. I am by no means suggesting that Mobil 1 is inferior in any way, but I wouldn't be at all surprised to find out that Mobil 1 offers the manufacturers some "incentive" to use their oil.

Generally, I believe this is true. Your new engine has contaminants in it from the manufacturing process and the break-in process is just starting. Your first oil change should come at an earlier interval than at any other time and will remove a lot of those contaminants. A lot of small-engine manufacturers recommend running conventional oil in their engines until the engine is broken in (50-100 hours) and then switching to synthetic if desired. That break-in evidently happens better with conventional oil.

There's also no sense in spending the money on synthetic oil right off the bat if you're going to be flushing it out early anyway.

Changing oils/detergents on older engines can be problematic due to contanimants or build up in the engine that the old oil didn't remove. When a new oil/detergent is introduced, it may cause any buildup to finally be dissolved, perhaps in chunks. More often, problems occur due to issues with the seals when changing from one oil to another.

NO, NO and NO.

I don't see the need, but I would guess it won't hurt as my Mitsubishi bus of 1989 was filled with only mineral oil from Japan, but at the first service I changed to synthetic and I sold that with 400,000 kms running like new.....9 years later....

Great people carrier, but I had seen a few that had had accidents, not good for the driver.....sold it to a Russian.....

Let's walk through this idea. IMO synthetic lube is preferred due its high lubricity in comparison to conventional oil.

The initial break-in of an engine is characterized as high wear event why would you want a lesser degree of lubrication during a high wear event?

In some cases you want a certain amount of wear to occur to properly seat the rings in the cylinder bores. That said, I wouldn't be surprised to find in this day of much better manufacturing tolerances and quality, that the old "break-in" may not be really needed anymore.

Synthetic oil not only has a much wider operating temperature range but up to 75% less wear on engine components. Sports cars often use synthetic oil in all transmission components and common automatic transmission fluids such as Dextron (GM) are fully synthetic.The down side is if you start using synthetic oil in the engine, especially on engines not originally designed for it you must continue to use it. Synthetic oil cause rubber seals to swell slightly and upon stopping its use may cause slight leakage of oil around seals. In colder climates the oil is far superior as synthetic 5W30 oil it does not get thick until you get to below -30F versus 0F for conventional oil. So for a state such as Vermont your car will have less wear due to poor lubrication during a cold start in winter. Personally I have used synthetic on all my cars, recommended and otherwise without a problem. Synthetic is lower friction such that the higher price is compensated for in improved fuel economy.

Dave

Are you suggesting that if I switch to synthetic oil in my full sized 4 door pickup, I will see a demonstrable increase in fuel mileage?

I bought one of those K&N (Disclaimer) air filters because my friend swore he got better mileage using one. I couldn't tell any difference in my mileage.

Do you have actual numbers?

You will not see a dramatic increase but it is my personal experience that it is there. It is only a few % but that is all it takes to compensate for the $15.00 greater price tag for an oil change using synthetic. For me living in Alberta Canada I did not have to use the car electric block heater until about -22F as the engine still turned over quite easily as the oil hadn't turned into honey. The big fuel savings is realized in winter as the oil is thinner and has less drag until the engine warms up.

Given the cheap gas in the states, you won't see as big of a savings as our friends over in the "Peoples Republic of Europe" where they tax the hell out of you for even thinking about glancing at a gas pump. But yes, there is a savings, and it will be enough to offest the higher cost of the oil several times over.

For what it's worth, I have run an '87 VW Jetta on plain ol' engine oil up to 250,000 miles changing it and the filter every 5,000 miles or so. No wear problems with it. We gave this car to our son to drive who was born 5 years after we bought the car.

I bought a 2000 Ford pick-up truck a few years back with about 95,000 miles from a guy who swore by synthetics and "advised" me that I should only use synthetics (5W-30). Well after running it a few hundred miles, I got tired of always adding oil at every fill-up. This thing just sucked down the oil. I got fed up and changed it over to good ol' 10W-40 from Sams Club. I only have to add about half quart over a 5,000 mile interval and we use the truck to tow our boat and toy hauler trailer.

Don't believe the Old Wives' Tales about changing from synthetic to mineral oil (or vice versa) will damage your engine. Utter malarkey. The synthetic oils today are miscible with mineral oils in fact you can buy synthetic blends if you want.

As for gas mileage, I tried synthetic oil in my '89 Chrysler mini-van when we were driving lots of highway miles. I wanted the extended change interval. I saw ZERO change in my mileage even though I went from a 10W-40 to 5W-30 synthetic. The fuel savings they talk about must be so far down in the noise, you can't tell.

Unless you are racing the engine, I seriously doubt you will EVER have a problem with temperature breakdown. A previous poster implies that localized temperatures may be much higher than the sump temperature. I'd love to see the data. Who has placed thermocouples in the plain bearings on crankshafts? Camshaft lobes? Etc?

I tow a 32 foot travel trailer 7,500-8,000 lbs with my 1/2-T Suburban with the 5.3L. We have towed cross-country, over the Rockies, in the East Entrance to Yosemite, the Sierra Nevadas and utterly flogged that poor little engine and transmission with extended full-throttle running at 4,500-5,000 RPM in second gear up long grades in the summer, with the AC on. Never a hint of anything nasty going on in the crankcase. Oil looked and smelled like it always did.

The point is, go with whatever you desire. As long as you change your oil and filter, you can't go wrong either way. The SynFaithful have their preferences, and I have mine. You can probably go longer change intervals with the synthetic. I have a co-worker that runs a TDI with synthetic. He only changes the oil when it needs it by an oil analysis. Periodically, he sends a small sample to a company that analyzes it for contaminants, viscosity, metals content, etc. I'm not sure of the cost but he is an engineer like me and doesn't waste money needlessly so I think the cost must be modest. The U.S. Army has had an oil analysis program for decades that has proven to save money on their oil changes and it also is able to warn of impending engine wear problems.

Brave Sir Robin -- First off I commend you for your critical thinking here. I was the poster who gave rise to your comment quoted as follows:

"A previous poster implies that localized temperatures may be much higher than the sump temperature. I'd love to see the data. Who has placed thermocouples in the plain bearings on crankshafts? Camshaft lobes? Etc?"

My comment was not based on rigorous testing or actual research findings but rather a good bit of experience with bearing technology and related calculations well sprinkled with information from a variety of sources. I did become a believer in synthetic oils some 35 years ago when I witnesssed what amounted to a product development miracle when an experimental trial with a synthetic oil turned a seemingly impossible problem with a high speed ball bearing application into a "walk in the park". My opinions as expressed here are the result of trying to explain what I've seen in the world of bearings and it is just that; opinion born of education and experience.

It would be interesting to explore possible technology for measuring local temperatures in a functioning plain bearing set. Having not kept pace in recent years with the world of tribology and the countless papers in that subject area I cannot say whether temperature measurement technology has advanced to the point suggested here. But I note that the currently available CCD and infrared electronic camera technology was beyond anything we could dream of 35 years ago. Experimental research in that area would be fascinating project today; although I suspect it has already been done and duly reported in the tribology journals. If not it would make a wonderful thesis subject for a phD in mechanical engineering or applied physics.

By the way, there are accepted mathematical models (closed form for 2 dimensional models) for calculating the temperature rise of liquid in a hydrodynamic bearing due to pure friction losses in the shearing fluid based on bearing geometry, loads, speeds and fluid properties. Additional temperature rise due to mixed film and "metal to metal" contact is what would be the subject of research and development of methodology for measuring resultant local high temperature "spots".

Ed Weldon

GA for a well balanced answer, that ties in with my small (minute in comparison) knowledge/experience in this area perfectly.....you know your "Onions" I do believe!

Hi Ed,

As an engineer, every thing you state makes perfectly good sense to me. I have a hunch that the operating conditions of ICE's even in extreme environments are probably not approaching the limits of today's lubricants. Just in my relatively short (30+years) driving experience, the cheapest oils you can buy today are so much better than even the best oils when I started driving. I remember scooping sludge out of rocker arm covers, glop in the oil pans, etc. I don't see that at all unless an engine has never had it's oil changed. It's amazing. It's also amazing that we routinely run engines 100, 200, and even 300 thousand miles or more without batting an eyelash. Advanced engine materials and lubricants have made this possible.

When I was a lad, it was not unusual to have to do substantial engine work at 50,000 miles or so, and if you "rolled-over" the odometer without a major engine re-build, that was something to celebrate.

My reasons for using inexpensive oil and changing it at about 5,000 miles is thus: At two dollars a quart it is about 1/3 the cost of synthetic. For a synthetic change interval of 15,000 miles it's more or less a wash cost wise. All my old oil goes to the recycling center so environmental concerns are assuaged. The one thing I do like about changing more frequently is that it gets me under the vehicle and I use that opportunity to "look around" for impending problems. I can check ball joints, grease any zerk fittings, look for fluid leaks/seepage etc. Also by-products of combustion get flushed out more frequently. Not that it has any real basis in science, but I like the sound of it.

If I were running synthetic, I would probably be tempted to use an oil analysis lab service to determine when to change the oil. With that information, you might be able to extend the change interval far beyond what most consider prudent intervals for synthetics. Cost savings then might be considerable.

Cheers !

First off, is your mechanic an oil expert or just a stick in the mud? most oil experts will tell you that synthetics are superior for many reasons not the least of which is the absence of unkowns and such found in non-synthetic oils. Typically you can go 2-3X as far on a synthetic. As for cleaning, why would a non-synthetic be better? Most likely, they have the same additives that do the cleaning. As my MB friend runs the shop at one of the worlds largest MB dealers, I trust him completely - he says Mobil 1 is the ONLY way to go. Make sure you use a quality filter that can last as long as the oil does.

Hay all, thanks so much; what a wealth of information. Since the car has always had synthetic oil and because of your help I'll stick with synthetic. My machanic is an old Vermont guy who is a genius with older (pre computer) cars especially diesels. He's got a 50 gal drum of Penzoil with a hand crank on it and he is determined to stick with it. I'll find a new machanic. To bad I like the guy. These days with the newer cars the shops with the computers own you. Almost makes me want to go back to the older Benz diesel wagon I once drove for 300,000+ miles before I sold it and bought this 2002 c240.

Thanks again.

Unless he's a total fool, you should be able to convince him to humor you and use the oil you want.

Pennsylvania oil is a wax base and all others are asphalt base, as I recall

However, Pennsylvania oil is scarce. I am not certain, but I think Quaker State and Pennzoil are no longer Pennsylvania oils.

PE bobimm

I have a Ford F350 with a 602 CID V8 engine. I am running Holley Projection that has a mechanical idle speed screw. I ran the engine until warm and then set the idle speed at 750 RPM on conventional motor oil. I then drained and refilled the crankcase with Mobil 1 and ran the engine until warm. With all adjustments staying the same and only the oil being changed the engine now idled at 850 RPM!!! The only logical explanation would be the decrease in internal friction due to the Mobil 1. I run Mobil 1 exclusively until last year when I switched to Castrol Edge. I ran a 2004 Jaguar XJ-R on Mobil 1 for a year and averaged 21.2 MPG, switched to Castrol Edge and found the car now getting 23.6 MPG average for the next six months with only the change in lubricant!! Synthetic oils ROCK! I am an engineer by trade and also serve as the Jaguar Car Club's tech expert for the past several years which a shop of my own and many Jaguars as Guinea pigs!!!

For anyone who has not yet caught the "Synthetic oil Bug", or is simply turned off by mechanics as mentioned here, I can only reiterate that I have 20 years firsthand personal experience of Synthetic oil usage in all of my cars.

Yes you might get similar results by replacing the oil and filter every 3-5,000 miles when using mineral oil, but I am still of the opinion that the full life of the engine, achievable with synthetic will still not be met, but that is an opinion not fact!

Look at the possible cost savings with synthetic:-

1) Often can be run for 20,000 miles with no problems, especially with engines having the "Oil computer", which is for most VWs since around 2000, or longer.

2) Only one oil filter per oil change. This could be a saving of between 3 and 5.5 oil filters....

3) Depending upon how you value your own free time if changing your own oil, or what the shop charges you for the work.

4) Time savings as well in only needing 1 of 4 changes or even 1 of 6.5 in some cases.....

Do not forget that a far smaller amount of waste oil needs to be dealt with as well!! Good for the environment!!!

Plus the fact that personally I have waited for at least one worn engine problem in all the cars (both petrol & Diesel) over the years (not all were new cars!!) and the often extremely high mileages many of them ran up.....never had a single engine problem!!!

I also notice that TDI engines, keep reducing the amounts of oil used between changes (remember also BIG LONG CHANGES!!) to as good as zero when above 110,000 KMs are on the clock!!! This stays stable to "God only knows when"!!, as we have sold the cars before the oil consumption started to rise again (assuming that is what would eventually happen!).

I know a Taxi firm in Vienna, that always run Skodas with TDI diesel engines, they sell the cars at around 5-600,000 KMs with a completely normally running engines.....no high oil usage or anything....

(Its for tax reasons the cars are sold off at less than 3 years of age they manage the best "write-off" price at that point!!)

All done on synthetic and in mostly slow city traffic......with an occasional run to the airport to pick me up!!!

All engines were running "completely" normally when sold. The last time I was there, a few years ago, they still had not had a single engine failure in their TDI fleet of 6 cabs.....which I almost forgot to mention, run 24 x 7, except for servicing.....

I know Synthetic is far more expensive than Mineral oil, I buy well off ebay, but as the saying goes, "Quality is never cheap!"....

Best of luck to all concerned, either way......

Your mechanic is trying to ensure you spend a lot of money with him. He's either a liar and a cheat or an idiot (or possibly all of the above). Either way, I'd find a new mechanic, one that knows that even low quality synthetic oil is far superior to any mineral oil ever made.

Synthetic oil differs from mineral oil in a number of ways. First off, it is a single hydrocarbon molecule, or a combination of up to three different molecules, not a mixture of different additives and hydrocarbons and tramp contaminants. so it does not have to keep all of those different additives in solution, so it has more excess solubility for waste products like sulfur compounds and carbon. it also does not oxidize at high temperatures like mineral oils do. It also does not gell up like conventional oil does at low temps (like those found in vermont!).

Secondly it has a higher breakdown temperature than mineral oil so it does not contribute to sludge build up, and it does not lose viscosity under extreme temperatures.

Some other articles on Synthetics:

http://www.carcraft.com/techarticles/synthetic_vs_conventional_oil/index.html

http://www.mobiloil.com/usa-english/motoroil/synthetics/synthetic_oils_faqs.aspx

http://searchwarp.com/swa7388.htm

http://www.jdpower.com/autos/articles/Synthetic-Motor-Oils

http://www.enhancedsyntheticoil.com/docs_amsoil_benefits.pdf

http://en.wikipedia.org/wiki/Synthetic_oil

One further thing, Your manufacturer's warranty is based on your use of the recommended oil type. if you use conventional oil, your warranty is void.

Hey you guys, I hope you don't mind if I butt into the conversation, but I've got two quick questions that kind of fit. 1) My grandfather always told me that changing oil was a waste of time and money. He only ever changed the filter and topped off the oil and never seemed to have any problems. (I'm not sure of the interval) Any credence to this? 2) If I was to flush engine and switch to synthetic on my 1999 dodge caravan (247,000 miles), would it swell the seals enough to slow oil leaks significantly? ( I just don't feel like tearing into it and regasketing.) Thanks

My Dad always said, "Oil is the life of your engine!" and that was before synthetics. Yes, changing filters is very important. There's a reason engines have oil filters, and when they clog, they slow the flow and that can lead to loss of lubrication and failure. When clogged, they can also rupture and let trapped gunk flow thru the system. Would you wash dishes in the same water and just filter out the grease and dirt? A few bucks for clean oil is cheap insurance.

Usually, a good make of engine will bypass the filter if its blocked. eg. if the pressure gets too high....

But relying on this is really bad/dangerous for your engine as there is generally no indication to tell you if the filter is being bypassed or not.......

At a minimum, the filter should be changed out, but a complete change with fresh oil at the same time is a really GOOD idea I feel!!

In the long run, its cheaper than a new motor as (completely untested of course) I cannot believe that an engine that only gets topped up and a new filter will ever last as long as one properly maintained.....but there again, if the amounts that get lost/burnt are high, then maybe I am completely wrong!!!

Of my last approx 8 or 9 cars that have run on Synthetic, none of them needed much topping up once they were well over 100,000 KMs were on the clock......so replacement was very low between changes....which implies to me that the "wearing in" stage was really slowed down as well.....indicates that synthetic slows down normal wear....

So there might be a case for running an engine on mineral oil for say the first 20,000 KMs or so, just to get it run in quicker, then switch to synthetic......though I have NO intention personally of trying this out!!!

I think I think the answer lies in an analysis of the drain oil at each change interval.

to answer your questions in order:

1) Sorry, but your grandfather was a fool. I would never EVER buy a used vehicle from him had I known that.

2) No, but by the time you've gotten to 247K miles, the seals are probably shot anyway and your engine wear surfaces have so much wear (especially if you've never changed the oil in it!) that changing to synthetic oil this late in the game is a waste of money, the sludge buildup from not changing the oil is probably the only thing keeping it from leaking like mad.

He changed his filters regularly, just didn't drain oil. I personally have never used that method. I also didn't say that I didn't change my oil. I was just curious to see if I could get enough swelling to stop the little drips.

Why don't you quantify your "drip rate", change to synthetics oil for 10,000 miles and report your findings.

Okay, why not? Just pesky little dime sized drips. Gotta add a quart about every 6 weeks, of course it's burning some oil too. In fact, maybe I'll start topping off with synthetic and find out the real truth on that also. I bought it 3 years ago, "cheap". I've changed the oil twice. That's it. Otherwise just gas and taxes. Oh yeah, two used tires at $25 apiece. I was kind of surprised to discover that I like me a minivan. Does that make me a wimp?

I don't think you are a wimp. I think you are a redneck.

Thank you

Next time you change the oil opt for a 20W50 regular petroleum based oil.

That will reduce consumption a bit. In Raleigh I don't think it gets cold enough in winter for the 20W to give you starting problems from the oil viscosity at low temps. And do it all at one time. The graph of oil mix viscosity vs. percentage of each of two different viscosities of oil in a mix is not linear. Rather it favors the lower viscosity of the two.

The amateur racing guys use higher viscosity oils in their engines because they tend to run higher clearances on the internal bearing parts. This is common practice among drag and street racers when they modify the 30-40 year old V-8's in their US made muscle cars. I don't know exactly what the Nascar guys do but given their enormous budgets their engine blueprinting practices likely involve the best of the best in machine tool technology. This means much more precise alignments of rotating parts which in turn allows closer bearing clearances and therefore lower viscosity lubricants. The result is less friction loss and more horsepower to the rear wheels. Pretty important in a sport where 5 or 10 hp can make the difference between winning losing.

I have good friend who has set several Bonneville small displacement streamliner records (one at 352 mph) using Japanese 4 cylinder motorcycle engines (mostly Suzuki Hayabusas). Even on his turbo engines that put out near 600 hp on methanol he uses the stock bottom end on the motors and a straight factory recommended synthetic oil. The level of precision in these engines from the factory allows that. This is a quiet side of automotive engineering that few car enthusiasts are tuned into. And it's something the Japanese are quite good at having jumped on the machine tool technology bandwagon early in their postwar rebirth. (Not that the folks at Mitsubishi and their counterparts weren't pretty respectable engineers and metallurgists long before that.)

Ed Weldon

Thanks Ed, I've put heavier weight oil in it and that does help. I guess you don't think much of our little experiment. I see your in the bay area, moved here from Santa Cruz about 9 years ago. It's amazing the thing is still running, I would say that using Mitsubishi engines was probably a good call on Chrysler's part.

changing to synthetics now would be a very bad error. Synthetics do NOT make seals swell, but they are more fluid and will leak through smaller crevices. so your leak rate will go up as will your oil consumption. your best bet would be to switch to one of the "high mileage" oils which are designed to be thicker and slow the burning of oil and help loosen rings stuck in the pistons due to carbon deposits.

At a company where I headed up the Operations and Startup crews (1996) we had some idiot who was placed in charge of making up the lube list decide to make the selections himself. That is always the function of the equipment supplier.

Anyway he specified synthetic oil for big Roots compressors, Lufkin gearboxes and the gearbox backstop. That was a hell of a mess as the equipment was designed for mineral oil and the gearboxes/backstops were a major problem.

When I asked Roots why they did this stupid thing they sent me a copies of faxes where our man had told them they were to use synthetic.

Moral of the story is to use what the manufacturer calls for. Don't second guess them.

Why would replacing mineral oil with synthetics cause a problem for Lufkin gearboxes? What was the effect? was it a chemical compatibility problem with seals? I know synthetics are not recommended for Wankel engines (which share some functional seal geometry with Roots type blowers) due to the lower viscosity/surface energy. So I can sort of see the problem there but not so much with the gearboxes.

Been 14 years and several projects past I am afraid. I remember well that I hung the clown out to dry for making up the list.

Seem like seals and the backstops were a real problem. The backstops had a cooling problem as I remember.

We also had problems with vibration on the gearboxes - Lufkin screwed up the design. We ended up (as per Lufkin instructions) placing steel slab weights on top of the boxes to give them more mass while Lufkin redesigned and manufactured new bıoxes.

The gear boxes, compressors and backstops were all new designs - the largest rotary lobe compressors ever built - with associated teething problems - all the manufacturers did a poor job and blamed each other.

Russ, bear with me, I'm not intimately familiar with Lufkin gearboxes or blowers except to know they make them for oilfield service and I have a fairly general idea of their mode of operation, but I've never had one apart in front of me. Please define what part you are calling the backstop. Are you talking about the rear thrust/seal surface that the roots impeller/worm gear rides on?

There is a 'backstop' on a shaft on the gearbox to prevent the machine from starting to rotate in reverse during the start-up sequence.

We typically used multiples of the compressors to get the total flow required for the process. One of three or two of five had the potential to start to rotate in the wrong direction. That would increase the starting torque requirement greatly with corresponding increased wear and tear on the motor, gearbox and compressor components.

ok, you mean a clutch or pawl that would lock the shaft if it tries to rotate the wrong direction. Like a Sprag Clutch?

Right