In Reply to: Bob; Question posted by Jeff on June 13, 2000 at 10:44:28:
A "hot" lap qualifying engine may use a very light 10 or 20 weight oil. A loosely built engine may use 40, 50 or 60 weight oil.
Mostly the true race engines that are "built" will use a single 40 or 50 weight "racing" oil that is not used but for one race, one lap or maybe one or two segments. These oils are often pre-heated before even cranking the engine. These oils don't have the detergents, etc. that we must have in a everyday driven car engine that must last a few thousand miles or more of crank-ups, stop and go driving, etc. They have lots or anti-friction qualities but very little other additives we need for more "regular" engines.
A true racing engine is a whole different ball game from our little "M" powered high performance I-6 200,000 miles (hopeful) street-driven engine.
: Why do you suppose race motors have greater tolerances than street motors.
: I worked for the NISSAN GTP team from '85-'93. I swear it seemed like they would run any straight 30 weight...as long as it was free. Valvoline, Chevron Delo, etc.
: Granted, those motors were putting out 1/5 the HP of a dragster but that is still a pretty light oil.
: : Very true! Or straight 50 or 40 weight "racing" oil without detergent additives and a lot of the other additive packages the oil producers must put into the everyday oils we use in "normal" car engines.
: : Most of these race engines are built with much wider clearances for the bearings, etc.
: : "Big Time" race engines of all types are completely and totally different from the high performance "M" powered engines in our M3s.
: : Bob ///M3
: : : Out of curiosity, I asked a bonofide racecar driver about oil weights, composition, and brand. Of course, the engines and applications are radically different from the typical M3 driver.
: : : When he drove the Lenco top alcohol dragster, they used straight 60 weight, and changed it after each 1/4 mile run.