[quote]there is absolutely nothing guaranteeing compatibility between any two sets of engine oil chemistry.

Actually the US government has required compatability on all motor oils sold in the US since the 1950s to protect their government and military vehicles.

[quote]Many of the additives don't play well with one another, and while your car won't blow up or stop running, it's very easy to seriously damage the anti-sludge, anti-oxidation, anti-foam, detergent and/or anti-scuff properties when you mix different oils.

Could you point me to a source making this claim? I would like to research this in more detail. My sister's first career was as a chemist and I would like to see if she has time to review this source.

Thanks,
Scott.

Are you talking about me or another post. Thanks Ron Parker













It Aint Over Until I Win

Hi Ron.
No I wasn't quoting you. I was quoting SlantSixDan. I would loke to research more about these incompatability issues.
Scott.

Nope. This is one of those myths that refuses to die. Everybody's heard one version or another of it, but nobody can ever produce any such a Federal regulation, 'cause it doesn't exist. Different versions of the story have been told about transmission fluids (false), antifreezes (false), engine oils (false), bearing greases (false) and brake fluids (almost true, because brake fluids are covered by a Federal Motor Vehicle Safety Standard, though silicone-based brake fluid is not compatible with glycol-based fluids, and both are legal and on the market).

The military protect their vehicles from the kind of damage you're thinking of by issuing their own specs (appropriately enough known as "mil specs") for every piece, every part, and every fluid—and procuring their own supplies, no matter where in the world they're operating.

Again, "compatibility" has many meanings. Obviously, all known engine oil is compatible in that you won't turn the crankcase contents into a solid mass of goo and seize up the engine by adding a quart or two of oil of a different brand or formulation. But, the additive packages are not all the same, and are not necessarily compatible with one another in the long run.
Probably your most accessible source for information of mostly decent quality on the matter of automotive tribology is www.bobistheoilguy.com .
Fantastic! Was she a petrochemist, or some other kind?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

There are documented performance increases in engines that are in good condition and running good synthetics, but they are small. They do run cooler, or at least the oils can transfer more heat than conventional oils. One thing about casual, informal testing: every car I have ever worked on ran a little better after the oil, atf, spark plugs etc. were changed, even if the new parts were not the best. I've seen this conclusion with splitfires. The car "runs so much better with them", sure it does right now, the old plugs were shot and fouled. New trans fluid can make a big difference compared to any old burned fluid too, in the torque converter and the clutch packs. Everything needs to be in good condition (Straight, round and tight) for synthetics to really show their worth. And it is maybe 2% at street rpm ranges, more in real race motors. You will probably see a bigger gain in performance with synthetic gear oil in the rear end of a street car than with motor oil. For me the cleanliness and durability are the biggest factors.

...

That's interesting. I looked at the link about Lucas Products. Eeerr..that doesn't look good. We've used it every once in a while around the shop, not anymore! We also run Schaffers?(duh, can't even spell it.) in important stuff(Great oil!) and Rotella in everything else. The Schaffers is my top pick over anything. Not expensive, and I've seen it do some incredible things.
Additives look like a waste of cash.....What about Slick 50? Any horror stories? It SEEMS like good stuff, but so did Lucas....

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225 Cubic Inches of Iron-Head American Muscle

225 bored .040 /.100 off block, Schneider Cam 224@.050~ .480 lift - Stock valves, blended bowls, Offenhauser intake with 500 Edelbrock carb

I once strayed and owned a Ford Ranger. Very nice truck at the time, wanted to" protect it". Bought the slick stuff, put it in twice and used that Tx-7 once, At 115,000 mi. the #1 rod let go. I sold the leftovers to Willard Buff, division 4 alcohol dragster hall of famer. Best damn mechanic I know. He called me to ask what in the hell did I do to this truck. He said when he pulled the pan, the build-up of crud was blocking the pickup tube,leading to the failure. I swear I changed that oil every 3000-3500 miles from the time I got it, used only Pennzoil the whole time, except for the last change, Kendall was on sale. Shouldn't be any crud right? Willard said engines got along just fine before PTFE, why ruin one with it? Learned a good lesson from that. Thought about trying that Z-max stuff.

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ifyoubegintothinkyou'relosingcontrol...it'salreadygone