Quote:
Originally Posted by Russell James
Depends on the honing method used. Modern plateau honing and modern rings do not require non-synthetic oil or any special break in oil. So on modern cars, synthetic is perfect to run from day one.
If someone rebuilds an engine with an older style of honing (sharp peaks) and older style super hard rings, then that engine would be better to break in with non synthetic oil.
All the performance LS engines come from the factory with Mobil 1 5w30. The V6 is regular 5w30 due to it's oil temp and intended use of the car is not going to require synthetic. The V8's if driven hard/competitively can easily get the oil temp above what is safe for non-synthetic oil. So they are required to run synthetic at all times from day 1 on.
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+1 as well special additives are needed if you've built an engine with a flat tappet cam. over the years, Zinc and other additives have been phased out of modern engine oils because it's no longer needed. But a flat tappet lifter and cam need the zinc to help harden the surfaces and crate desired wear patterns. So nowadays you need break in oils or additive if you've built an engine.
Modern cars "break-in" period is almost a non issue. Machining and material techniques have nearly eliminated the need to break in an engine like you used to.