Chevy recommends 5W30W oil for the original LT1 engine. My rebuilder reccommends 20W-50W conventional oil for the rebuild. Any thoughts? My feeling is that I should use conventional oil for the first 10K miles and switch to synthetic. I got 157K out of the first engine using 5W-30W synthetic.

 

5w-30 dino oil for 3k then switch to syn... always use dino oil for break ins... and 20w-50 is way more then an LT1 needs unless ur clearences were made "loose"

 

5w30 is CAFE talking, read the manual 10w30 is fine for warm weather, actually I think it is good down to 0F according to the owners manual. 20w50 sounds thick I would talk to the builder and ask what he setup the clearances for, if he set them to near stock then this conversation can continue, if he set them loose for thick oil then I guess you need to stay thick, and consider using someone else next time.
I know one member here raves about a specific 0w30 maybe he will see this and speak up as he knows much more about oil than I. I am using something that would make you all think I am cracked so I will wait till I drain it and have it tested before I recommend it.

 

I'm confused. Why is it that everybody raves about using syn. oil. but almost everyone I read about on this board has engine failures such as spun bearings and ring failures. I have used valvoline 5w-30 or 10-40 (depending on the manufactures recommendations) on all my cars in the last 20 years. Including my 1970 Dodge Challanger r/t, '67 chevelle s/s and other high performance cars (not to mention my current z/28 that uses 5w-30). With millions of miles driven not one of these cars EVER had a oil related failure or excessive wear. The secret is frequent oil changes and not leaving dirt in the engine.

Does anybody on this board have a z with over 200,000 miles and no engine problems (Including compression).

 

0-40 synthetic mobil 1

 

15w-50 m1 for me used on 3 LT1s I owned, supercharged and naturally aspired....

 

The spun bearings are usually people who did a cam change and then turned the motor well above 6k rpm. Ring failure is usually associated with nitrous or supercharging. The oiling system in the LT1 is more than adequate for the motor. FWIW, I use either Mobile 1 or Royal Purple in my LT1 and I haven't had any problems yet (knock on wood). I do advise you to run regular dino oil for the first few thousand miles so the bearings will seat properly, synthetic is too slick and won't allow that which usually leads to a spun bearing as well.