just got my ls block rebuilt with new pistons, rings, rods, bearings. what weight oil should i use? thanks.

 

i would use valvoline, synthetic or conventional 10w30 or 5w30. Whichever you use, make sure you continue using that.

 

I've heard it's best to use straight mineral oil for the first oil change. Even just regular oil for the first 1000 miles, then change it and look for metal if there is none then you can replace with synthetic or whatever you want. Just what i've heard, i'm not a mechanic but it makes sence to me