I just rebuilt a 355 lt1 and i want to use mobile1 synthetic oil 10w30. Is that good or should i use the conventional oil?
I think that will be a fine choice if using a roller cam, and possibly OK with a flat tappet. I know VR-1 Valvoline synthetic is still OK (I checked out ZDDP content on their website before using it in my Pontiac 455) for flat tappets but not sure about Mobil1. I believe you'll want to use a conventional oil (plus a break-in additive) for the break-in period (for proper ring seating) then switch to synthetic after that. Don't take that as gospel, I'm just an old bodyman. An engine builder will probably stop by soon and inform us both what the deal is.