Synthetic/non-synthetic oil compatibility.

Good, no great question J Deuce. And the heck if I know! I had an uncle that would only use the same brand of oil. I heard another guy say he wouldn't mix any two brands. If he needed to add he changed it all. Go figure.

proudly being of absolutely no help,

cr3

Hi Charles,

That's okay. Thanks for weighing in anyway.

I've never used systhetic oil but I've heard many good things about it so I'm thinking about switching over to it. Got 50 k on my 1997 Dodge Ram, 5.9 liter engine and have always changed oil & filter every 3k - 4k miles. Love my truck but it's really a gas hog.

Maybe synthetic will get me a few 10ths of a mile better mileage. Anyway I'd still like to know about the compatibility thing.

Regards...

the oils are fully compatible both ways. Switching back is also 'friendly'. Earlier 'synthetics' tended to suck the seal softening process oils out of the seals, leading to leaks. Now they add 'seal swelling' additives to the synthetic stuff. There is very little molecular level difference between the oil molecules in 'synthetic' and the 'hydrocracked' stuff used in 10W30 and such. They look and perform nearly identical in all services. The difference is in the additives, with 'pure synthetic (polyalphaolefins) having much worse detergency and solvency for crud. In fact, the 'additive diluent' for synthetics -up to 15% of the total vol, are a lower quality base oil than that used in 'conventional' base oil formulations, just to increase the solvency to keep the additives from coming out of solution. Some highly advertised synthetics (first letter of name in middle of alphabet) have significantly lower levels of anti-wear additive. This has led to camshaft failures in some engines. The highly promoted 'oil service indicator' system in BMW and MBZ led to very high cost warranty replacement of engines. Frequent oil and filter changes are CHEAP. LOTS of advertising long enough--makes people believe, still does not make the case technically. Many more NASCAR, Indy 500, Formula 1, drags, etc have been won every year on 'conventional' oil than 'synthetic. You can book it that IF synthetic really provided a performance edge, everyone would be running the better oil. F-1 engines now must last 2 entire races-including practices and quals, or the car is penalized severely. But they only rev to 19,000 RPM and races seldom last more than 2 hours Why are you using the 'high priced spread? Advertising gottcha? Unless you are racing, or driving in the arctic, or drive from the hot dessert to the frigid snow fields daily, premium quality 'conventional' oil will provide just as good service. You still must change the oil at MFG suggested intervals or sooner or void warranty. Premium multi-grade changed every 4000 miles is much better long run than synthetic changed every 15K miles.

Wow...nice answer.

I'd just like to chip in with the taught that such a huge engine must be pretty low stressed in convention use. I'd have thaught that just about any lubricant would probably do...a few litres of used oil from the burger bar?

The Fords and Chevys are the only ones stressed. (when they get too close to the big Ram).

dodge can't keep up to ford and is at least 15 mile behind chev.

Speed kills so drive a dodge

I work for a VERY major oil company. I know the manager of a blending facility where they make all types of oils. None of the lube chemists I know run synthetic in their own cars. Due to poor additive characteristics they need to change their oil more often to get a fresh dose of chemicals. It is the chemicals that neutralise acids that keep oil 'fresh' in your truck. Burning hydrocarbons (gas, diesel, natural gas) produces acids that end up in your oil.

Lack of lubricity doesn't kill engines (in our daily use) but chemical attacks do, and it is likely chemistry that breaks down oil's ability to lubricate. Notice the words CHEMICALS used many times, not lubricity. If an oil losses its lubricity, you will likely find a chemical (additive) reason behind it. If you start having more wear, you may find a chemical reason (additives) behind it (acids etching your surfaces).

In a previous life, I evaluated synthetics for a large pipeline contract where we had 40 big 8,000 HP diesel engines. Oil purchases were millions of $$ each year. All the big oil companies offered their synthetics and when we were done with meetings I asked all of them what type of oil they ran in their own vehicles. Mineral oil ! (the normal stuff). Not synthetic ! I never bought the synthetic for the engines, but did buy it for the huge gearboxes and pipeline pumps with large high energy bearings.

My only reason to use synthetics EVER in my career is pour point. It pours at very very low temperatures (-20 F pours the same as + 70 F for example). So I use it in cold weather gear boxes and such things where there is no combustion products.

The molecules of synthetic are all shaped the same. They begin with mineral oil and 'select' the same shape molecules (in layman terms) and they all lay down very flat on the surface and lubricate better and remove heat better due to this surface contact. And since they are all the same shape, they align themselves and pour better (they don't stack up). Viscosity improvers for mineral oil (Paratone for example) are sticky and cause pouring problems at low temperatures.

For synthetics, additives have a hard time migrating into these closely packed molecules. This is a real layman explanation and some chemist may butcher my explanation here.

Bottom line: Don't fix it if it ain't broke. Don't swtch. It'll cost you more since you'll need to change oil more often (maybe). Sign up at a Caterpillar dealer for SOS. Scheduled Oil Sampling and change your oil ONLY when the anaylsis tells you to do it. About $15 per sample. They have a kit for drawing oil up your dip stick into a sample bottle. You can trend wear patterns and see what is happening in your engine, trans, differeintil, etc.

Try explaining this to your wife: "I saved $0.003 per 100 miles by using sythetic just before the $7000 rebuild"

Run the math. It will not pay out.

Hi Petro,

Thanks for all the good info (thanks also to Keith). I think I'm now convinced to stick with conventional oil.

You said "Due to poor additive characteristics they need to change their oil more often..."

Seems like with the extra cost of synthetic over conventional, changing oil more often would be entirely cost prohibitive. I thought one of the selling points of synthetic was that you don't need to change it as often. Marketing hype I guess.

Anyway, good answers guys.

-John

My last 4 diesel cars required Synthetic, longlife I on the first, Longlife II on the second and the last two need Longlife III, that was specified by the manufacturer....anything less and the warranty was gone!!

I have only run just over 120,000 KM in the first three cars, with no problems and very little oil consumption. The fourth car has about 55,000 KM at this time and is looking the same, less than 1/2 liter of refilling in 15,000 KM.....

Nobody has mentioned the fact that Synthetic evaporates when overheated and does not leave carbon residue as many normal oils do, which is why Synthetic works well for diesels, especially those with Turbos.....

A Taxi firm I know in Vienna use only synthetic and they sell the VW and Skoda Taxis, with around 550,000 KMs still in a normal running condition, not burning oil or any other complaints!!!

That is putting your money where your mouth is!!!

Current score:

Use synthetic: 1

Don't use synthetic: 2

In the USA, you are too used to changing oil every 5000 KM, so there is little point in having an oil that can stay in the engine for over 30,000.....

But it does help to reduce the amounts of waste oil that has to be got rid of!!!! So one should also review the environmental aspect as well.....

Having used Synthetics for as long as they have been around with no problems on both petrol & diesel motors, I am convinced!

<too used to changing oil every 5000 KM>

Wow! The oil service interval for the Volkswagen Passat says oil and filter every 16000km!

....I was talikng about US made cars.......

There was a recent CR4 discussion on this same point and many, many US citizens will not budge from cheap oil being changed too often.

Of course if you have a European or japenese car, the intervals are longer and the required oil quality is much higher.

My VW Touran knew when the oil needed changing, usually between 32,000 35,000 kms....a modern car!! Longlife III !!

Hmmm . . . $20 mineral oil change every 3,000 miles instead of $40 synthetic oil change every 30,000 miles . . . 180,000 total miles means savings of $960 using synthetic, but $3,000 engine rebuild wipes it out and puts you over $2,000 in the hole.

Oh i forgot to mention something, I was saving it till someone made the mistake you just made about the life of an engine.

My Mitsubishi L300, managed from new, with Synthetic oil (the early version in europe, I have forgotten the make!) to clock over 400,000 miles. The engine started and ran like any other with say 50,000, it used only about 1/4 liter per 15,000 service interval.

I had no problems selling it at 9 years old and got back 8,000 DM with a new price of just under 30,000 DM......not bad eh ?

....AND I almost forgot, it was poisoned at around 160,000 kms with Agri-petrol in Italy, an old Mafia trick, but it got to Switzerland from the Mediterranean , just being topped up from time to time with water......any less good oil than fully synthetic and the engine would have seized up!!!!

It never ever had the head off either for any reason whatsoever!!

Lovely stuff Synthetic!!

I feel that most 90 BHP 2 liter petrol engines with that mileage and normal oil would have needed a rebuild well before.....a big old V-8 with little BHP, would probably also make it on any oil!!

Hi Andy,

I can see you're a believer in systhetics. What do you think about switching from one to the other, or mixing the two together?

Keith says it's okay to mix the two.

If your engine manufacturer specifies only Synthetic, never mix, you will kill any guarantee you may still have. I always carry a liter bottle in the car as Longlife III is not everywhere.....as a "just in case" sort of thing!!

If the engine is relatively new AND still in very good condition, but the manufacturer does not care, change to synthetics (not the word that you wrote by the way, look at your post "systhetics", UGGHH!). It will extend the engine life....

If your engine is brand new, go for the best synthetic you can find if you anticipate keeping the car for a long period and do not want to ever pay for an engine rebuild....read your engine guarantee carefully before doing anything.

If you own an aircooled engine, stay with what the manufacturer recommends only (VW Beetle for example).

If your manufacturer does not specify Synthetics, you can mix normal in if the level drops alarmingly and the right Synthetic is not available.....but why do it except in an emergency?

I have had 6 vehicles since 1990, all ran on full synthetic, none of them even had the head off, none had major problems of any sort.....all used VERY little oil between services....

"look at your post "systhetics", UGGHH!"

Little typo there Andy. "Systhetics", hmmmm, sounds a little like aesthetics or maybe even calisthenics, or something.

Anyway, as I said in an earlier post (#2), My truck is a 97 Dodge Ram, 5.9 liter, petrol, w/ ~50 k miles on it. Uses almost no oil and I change it every 3-4k miles. As has been stated by others (Del, for one), switching to synthetic (spelled it right that time) probably won't enhance performance or mileage all that much. I was really just curious about the issue of using synthetic.

Regards,

-John

P.S. Don't know if others have a problem with wireless keyboards or not but I find that I can easily get ahead of the thing! If I do, letters get left out, transposed, etc. I do try to use spell check religiously, but sometimes I forget.

For you it may not be worth it, you need a value, preferably from the manufacturer, as to how many miles you can leave between services. Usually its double when you were using a good multi grade before......that is very aproximate....

VW Diesels are allowed over 30,000 KM per filling.....but a computer keeps track of how you are driving etc....

My keyboard does the same a few weeks before it needs new batteries, about 24 months....

The red lines remind me to use the checker!!

As Sasol, Ltd has probably more experience in this area than anyone on the planet (they have been producing synthetic since the 50's) I would recommend you email them for advise.

Good question! I was also going to ask a similar question about synthetic oils. I have also used synthetic oil in one of my diesel car before. My question would relate more as to what happened to the much talked of TEFLON additive in some synthetic oil brand? There have been counter claims that it does not work at all as claimed.

nulon products are widely used for engines antiaging , PTFE coating ones for certain amount of traveling distance is quiet effective with synthetic oils that too comparable to mineral oils .

I do not know much about automotive oils, but I would under no circumstances use any oil advertising the addition of teflon. Teflon flakes swell, get stuck in filters, lay down on journals and destroy the ability to form a satisfactory oil wedge. (If it is your intention to empty out the oil and then drive your car around then the Teflon may function as advertised, but this is not a normal practice).

The oil companies will tell you that their "synthetics" are compatible with conventional oils. This is true in the laboratory when you mix a beaker full and stir it, could be true in automotive oils but I very much doubt it, and has proved to be definitely not true when used in turbo machinery. The change from Group 1 to Group 2 base oils has caused endless problems for operators of large steam turbines and gas turbines in particular, due to mixing of the different base oils.

As I understand it, "Synthetic" oils have better oxidation stability (produce less varnish) than conventional oils but have a much reduced ability to carry the sub micron products of the oil degradation in suspension.

My view would be simply that for the ordinary motorist a good quality conventional oil is perfectly satisfactory. Use synthetics if you feel conditions warrant them. Do not use synthetics oils in older vehicles, in fact I would only use synthetics from the start of the engine life, and never ever mix the two.

I hear what you say, I personally have never used any oils with Teflon in them, I see no point at all and I can well imagine that what you say is perfectly true on that score....

As my car has not got a steam turbine or similar, I doubt if i need to worry on that score either....

I have just had 5 cars of mine (and a few of my wife's too) that have run probably near to 1.5 million KMs (rough guess only, could be more!!) over the last 16 or 17 years and we have NEVER had to open up an engine, except when changing the drive belt for the valves......all on synthetic oil from several manufacturers....

I cannot for the life of me imagine that the oil multis make it just for fun.....but whatever, my cars all have run well on it.....its something I just take for granted.....where I have had further contact with my cars (only 2) after selling, several have clocked up double what I put on the clock again and I have not heard of any problems of any great degree.

I always tell the next owner that I used only Syth and original manufacturers filters....(I once nearly had a bad go with a non OEM filter, but from a good company!!)

But as ever each to his own......

Hey guys, here is a good page about oil additives, I copy one paragraph to highlight what it says.

"There are about 50 other products on the market which make similar claims, many of them being just duplicate products under different names from the same company. The price for a pint or quart of these engine oil additives runs from a few dollars to more than $20. Do these products do any good? Not much. Do they do any harm. Sometimes."

But for the complete page ,please go to http://skepdic.com/slick50.html

And this one link has all the answers to the question about mixing synthetics and non-synthetic motor oils.

Mixing Mineral and Synthetic oils - the old and busted concepts

For the longest time, I had this to say about mixing mineral and synthetic oils:

• If you've been driving around with mineral oil in your engine for years, don't switch to synthetic oil without preparation. Synthetic oils have been known to dislodge the baked-on deposits from mineral oils and leave them floating around your engine - not good. I learned this lesson the hard way! It's wise to use a flushing oil first.
• If you do decide to change, only go up the scale. If you've been running around on synthetic, don't change down to a mineral-based oil - your engine might not be able to cope with the degradation in lubrication. Consequently, if you've been using mineral oil, try a semi or a full synthetic oil. By degradation, I'm speaking of the wear tolerances that an engine develops based on the oil that it's using. Thicker mineral oils mean thicker layers of oil coating the moving parts (by microns though). Switching to a thinner synthetic oil can cause piston rings to leak and in some very rare cases, piston slap or crank vibration.
• Gaskets and seals! With the makeup of synthetic oils being different from mineral oils, mineral-oil-soaked gaskets and seals have been known to leak when exposed to synthetic oils. Perhaps not that common an occurrence, but worth bearing in mind nevertheless.

Mixing Mineral and Synthetic oils - the new hotness

That's the thing with progress - stuff becomes out-of-date. Fortunately for you, dear reader, the web is a great place to keep things up-to-date, so here's the current thinking on the subject of mixing mineral and synthetic oils. This information is based on the answer to a technical question posed on the Shell Oil website. There is no scientific data to support the idea that mixing mineral and synthetic oils will damage your engine. When switching from a mineral oil to a synthetic, or vice versa, you will potentially leave a small amount of residual oil in the engine. That's perfectly okay because synthetic oil and mineral-based motor oil are, for the most part, compatible with each other. (The exception is pure synetics. Polyglycols don't mix with normal mineral oils.) There is also no problem with switching back and forth between synthetic and mineral based oils. In fact, people who are "in the know" and who operate engines in areas where temperature fluctuations can be especially extreme, switch from mineral oil to synthetic oil for the colder months. They then switch back to mineral oil during the warmer months.

There was a time, years ago, when switching between synthetic oils and mineral oils was not recommended if you had used one product or the other for a long period of time. People experienced problems with seals leaking and high oil consumption but changes in additive chemistry and seal material have taken care of those issues. And that's an important caveat. New seal technology is great, but if you're still driving around in a car from the 80's with its original seals, then this argument becomes a bit of a moot point - your seals are still going to be subject to the old leakage problems no matter what newfangled additives the oil companies are putting in their products.

Complete info on this site:
http://www.carbibles.com/engineoil_bible.html

Hi rupertal,

Good links. Thanks.