Well, it seems like a case of the blind leading the blind. My friend has been helping me maintain the car, and for some reason it overheats, misfires, and I've got 20-50 synthetic oil in my car that I overpaid for.

He said it would be fine, but I've heard otherwise from the local performance shop around here.

Should I get it changed out STAT (it's at a shop getting a new clutch installed) Or should I wait till next season? Insurance runs out in a month and a half, and I'll probably drive the car about 1000 miles in that time period, then it will sit the winter, till next summer. Should this oil be ok for 1000 miles? (It's got about 500 miles on it) Or should I get the shop to put some proper oil in?

Thanks.

 

I'd change it out. No sense in taking any chances. I imagine it would be way too thick for your car. Hell, diesel pickups generally run 15w-40.

 

my 93 was just drained of its 20w-50 and i can tell you what it did to mine. it only dropped the oil pressure. but if you start your car up during colder wheather then you are taking a risk. 20w50 is thick already but when its cold that stuffs thicker than normal and after awhile can ruin a stock engine.

 

In the hot weather of summer I don't think it will do any damage. As far as "the right oil" well it depends on what you consider right some of the most popular stuff is actually to thin. If you want to stay synthetic try the M1 0w-40 or 5w-40 there are other showing a little better results but there are very good and easy to find.
Offshore like in Austrailia they speced 15w-40 for the Lt1, imagine the cars sent to the middleast got the same recomendation the b-body was popular over there so there were a number of LT1s that ended up there. If you go to the oil manufacturers sites sometimes you can find a oil selection helper and if you really look you can find it where it will allow you to choose a location other than the U.S., spec somewhere outside of North America and the oil weight recommendations get thicker ina big hurry reguardless of the vehicle. We have CAFE to thank for the5w-20 5w-30 speced in everything today.

 

If it's a stock motor it's designed to run 5W-30 or 10W-30 because thats what the bearing clearances are set for so why run a higher weight?

Bret

 

What about a motor with 100k miles on it? Bearing clearances arent what they used to be.

 

I'm running 15-50 in mine right now, but it's synthetic, plus the weather's really hot. I think 10-40 is probably the best for an LT1 in hot weather, the 30 weight seems too thin to me.

A thicker oil will also give you more protection if you spin your engine up quite a bit. A few magazines have done articles on that, it was actually worth a few hp on top (better stability) with a loss of a few on the bottom.

Anyway, I've had no problems. But I don't think I've started my engine with that oil in it at less than 70 degrees. I'll most likely go thinner again in September.

 

Analysis of wear metal content in used oil proves that the LT1 and LS1 for that matter prefer a thick 30wt. to a thin 40wt. The ever popular 5w-30 and 10w-30 M1 fall right at the bottom of the thin end of the 30wt. range and analysis proves these oils are less than wonderful choices for these engines. Arguing with this is the same as arguing with dyno numbers or track times, this is the real evidence of what oils work best. In M1 you need to go with one of the 40wts. Amsoil will be fine in 0w,5w or 10w-30, German made Castrol syntec is PERFECT in 0w-30, most dino oils will probably be good in 5 or 10w-30 as they do run thicker on average than the M1 offerings. OEMs are thinning out oil specs without changine bearing clearances everything I have read on the engines Honda and Ford are specing 5w-20 in is that the clearances are the same as the 5w-30 motors a year or 5 earlier. OEMs have things to worry about other than absolute longevity hence the specs of less than perfect oil weights.

 

My thoughts exactly... Good protection.... no aditives necessary.... peace of mind.