Engine Oil Mythology

71DodgeDemon340 said

Not sure if full synthetic oils would do well in a older un touched engine but my engine builder who built my 340 reccomended mobil 1 full synthetic and says he does for all his engines. its nice to have a engine builder with full synthetic in mind when they are bulding it. but really on a rebuilt engine you should be able to use either. as long as you use proper break in oil it should be fine.

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Absolutely.
Great to hear your engine builder is on board for the full synthetics in your new build and is doing the machining to accomplish it.
An older broken in already engine in good shape would do great with synthetics, but, a worn out engine or one that was prepped the old way wouldn't break in properly until the first couple of oil changes with dino oil.
It's all about cylinder prep and the style of rings used.
Yes, i have seen first hand the results all of the way around, and i'm convinced that synthetics are the way to go if everything's right.........