As an Amsoil Dealer I have had some experience with rebuilt engines and
synthetics. I have rebuilt four MGB engines and now use Amsoil in all of them.
Synthetics are so good that they MUST NOT be used during break-in. In
a B engine I run about 5000 miles before switching over. After that I go
about 10,000 miles between oil changes. Synthetics reduce wear (by large
margins), Are less prone to evaporate, do not create sludge, keep the engine
cleaner, have a thicker film, and do not break down (shear) with heat (until
very high temps). There is plenty of information out there about how good
synthetics are. I use synthetics in all Five of my MG's.
Newer cars have a type of parkerizing applied to the engines. I'm not
an expert on this. I think this would have an effect on break-in. Also new
cars are made better with tighter tolerances.
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