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?
Chevyboi22 Break your new engine in on Regular SAE 10/30-10/40 and if you didn't install a roller cam on the build, put an additive in the oil. Put atleast 5,000 miles on your engine before using the Synthetic oil.... Either for the synthetic or the regular SAE oils if using a flat tappet cam use an additive. Just my 2 cents. I believe they are ripping us off at $8.00 a quart of oil for the additives. I have yet to loose a cam even on the break-in procedure. I'll tell you we use. 15/40 Diesel oil. For my 86 Monte Carlo. Been doing it for years....We use it on the dyno for cam break-ins. Like I said my 2 cents. I'm not going to make Joe Gibbs richer...LOL...Bob
Woops, didn't see the double-thread posts. I answered the other one. Howdy, Bob cut-n-pasted:"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."