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I've found several other questions on here that answer, "what's different between synthetic oil and regular oil?" or "Can I use X oil in Y car?", or similar, but nothing that quite answers my question.

I have a car with a high revving engine that requires 10w-30 full synthetic oil. My mechanic (who primarily works on racecars) uses Valvoline, but several other people I've talked to swear up and down that if I'm not using Mobile 1 or Royal Purple or insert-your-favorite-brand-here, that my engine isn't going to last as long or perform as well. When I'd ask about the difference though (they're all 10w-30 full synthetic, right?) none of them could give me an answer. I'm aware that certain synthetics might be parafin based which would gunk up the works, but I don't think any of the above examples are actually parafin based.

TL;DR: Is there really a difference between different brands of full-synthetic 10w-30 oil?

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Sam, Chemistry isn't my strong suit, but when it comes to synthetic then no, they are not created equal. I know you're not looking for a shopping recommendation, and I can't give you one anyway. What I can say is that the additives the manufacturers use are selected for different reasons (high temperature additives for races cars, different additives for older high mileage engines, etc), so knowing that will help you make the right choice.

From putting 150k of the 200k miles on my current daily driver I'll tell you that initially I used Valvoline high mileage religiously, but when I need oil (slow leak) in a pinch, I'll pull up to the nearest gas station and grab the cheapest 10w-30 they got, and like I said -- I'm somewhere in the vicinity of 200k miles (digital odometer died) and the engine runs smooth if I do say so myself.

I've always (usually) followed the advice: keep the oil changed. You probably know after so long the oil will change it's viscous properties, which can be bad for the engine. The different additives can delay or (as a result of achieving another feature) speed up this breakdown.

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    Good to know; thanks. I'll have to find a place where I can research the various addatives and see if any of them are worth sticking with. It's hard to find any info that's not just marketing garbage.
    – user3729
    Commented Sep 20, 2013 at 14:35
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    @SamWhited some really good, well informed information at bobistheoilguy.com
    – mac
    Commented Sep 23, 2013 at 19:54
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Most oils have proprietary additives.Mineral based oils contain sulphates that can be damaging to "yellow metals" i.e. copper and brass etc...(an issue with gearboxes) Synthetic oils generally do not.Follow vehicle makers specifications.

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