[320hpPony?]

I just put my paws on a 94 Trans Am with the LT1 in it.She's got a mild cam,fully adjustable real time "chip"(really it's a hand held control unit),headers,MSD ignition,more than my brain will register to write down for y'all at this drunken moment! Question is this though,since I didn't get an owners manual with this car what wieght oil should I out in it?I use 20w-50 in both my my 87 GT pony and my 78 Monte Carlo but I know that newer cars take the lighter 5w oils.What do y'all think would be the "heaviest"oil I could put in my car that isn't too heavy for the oil pump?

[mdvaldosta]

I prefer 5w30 in all "normal" vehicles. 40-50wt oil is just too thick (even for an 87 Monte Carlo). Lighter weight oil causes less drag, offers better fuel economy, and protects better in my opinon. 20w50 is last leg kinda stuff, something to put in an old truck with a smoking engine, heh. Some other may disagree but that's where I stand.

[320hpPony?]

preciate it, Gm tech's say 5w-30 too so that be da ansa right?20-50 in my monte works great,no sludge(I change oil once a month though! not because i have to but because i want to and it always looks like honey).

[Bossman351]

5w-30 is recomended from the factory. The reason they recomend a lighter oil is b/c the tolerances and clearances are a lot tighter in newer cars. If you have ever been to a parts store and seen the Lucas display, try it. You will notice that the Lucas oil does coat better but also notide how much harder the little crank is to turn. That is whats going on inside your motor. Also notice that the "plain" oil coats to the top gear, its just not as thick when it gets there.

[XxViSiOnxX]

well in a sense both are right but the weight of the oil will be determined by the amount of miles the car has? normally 5w weight is for cars will less than 100k miles which i may be wrong but in the range and anything after that would be 10w or 20w thats how i was shown, my grandfather was a mechanic all his life and thats how he showed me and his cars purred like kittens...!

[Monark]

I know this is a little off topic but we're on the topic of oil and I don't want to make a thread about it. Is it bad to use 5w-40 or 10w-40 on a car thats supposed to be 5w-30 or 10w-30? If so how bad? The car I'm using right now uses 10w-40 but its late 80s BMW straight six with 130,000 miles so its a little different than a 2005 Mustang GT with 30,000 miles.