> Actually my understanding is that oil has gotten worse recently,
> something about removing the additives that protect against friction.
That depends on the engine.
Since about API SJ (ten years ago) oils have been losing their
zinc-based extreme-pressure additives.
This is a response to how US automakers want to handle EPA catalyst-life
requirements.
The Euro automakers haven't entirely agreed with this approach.
For modern engines with low-tension rings and roller cam followers and
etc. it doesn't matter.
For older engines, especially flat-tappet pushrod engines but really any
engine with a lot of bits that slide on each other under high pressure,
it can be a very bad thing.
>> It's 2011. There are better ways to chose your oil change interval
>> than "I thought". Used oil analysis can tell you an awful lot about
>> the actual state of the oil. It's a waste of money and natural
>> resources to change your oil before it's needed, and changing it at3k
>> because that's what you've always done is firmly in the wastefull zone.
>> Again, it's 2011, oil and oil additive packages are way way better
>> than they ever have been. Enjoy living in future.
If you want to pay $1.49 a quart or whatever no-name generic oil is
going for, it's no better and maybe worse (see above) than it's been for
a long time.
If you're paying $7.50+ a quart for the good stuff, then for modern
engines at least it's better than what we've had in past years.
3000 mile changes make little sense, but whether you should be changing
at 5000, 6000, 8000, or whatever depends on the car and the oil.
The Germans like big (7, 8, 9-liter) oil capacities, VERY stringent oil
specs for high-temperature viscosity stability (ACEA A3/B3, BMW
LL01/LL04, MB 229.2, VAG 502.00) and 12-16K oil changes - we've got
three vehicles that fit in that category and I change them all at 7-8K.
Japanese and American mfrs go for smaller sumps, much thinner oil for
better CAFE results, and shorter change intervals.
And if you've got a modern particulate-trap diesel, you've got a whole
'nother set of specs to deal with.
John.
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