Originally Posted By: oil_film_movies
All this trouble: "change the oil to 15w50 (ZR1-LT5) before track day pre-race but don't use 15w50 on the street..."
and/or "We're just going to tell you to put in thick-ish 0w40 and say its good for most racing too"
is not necessary.
You can keep your relatively thin street oil in the sump and still race at high enough HTHS levels by using a
thick addition to your sump, adding base oil with PAO+POE+GroupIII, maybe with a little extra ZDDP too. Add before track day.
Mobil and GM could provide guidance on how much to add, but it could be done so someone doesn't keep dumping tons of barely used sump oil for track day.
Certainly phosphorus (catalyst-killing) levels could be avoided, possibly by adding more polymer esters instead of something which boosts zddp too much, so you could use the race-oil concoction on the street for a while after track day until change time.
Saves trouble, cost, waste, and time.
Very similar to Joe Gibbs HVL (
http://www.drivenracingoil.com/newsfiles/HVLMSDS.pdf )
It's all just a ruse. Even if you do run catalyst-friendly oil, if you do enough track days, it will kill your cats anyway. I killed two sets of cats in my LS1 Camaro in four years of track driving, then gave up on them. The only place that you could run your 650 or 750 HP Corvette to enjoy its performance to the maximum is on a race track. In that environment, it is easy to burn a quart in a few hours of track time. In comparison, street driving entails very little oil consumption, so the high-zddp 15w50 would not be damaging the cats very much. GM may say to change back to ILSAC oil for street use, but that is just to make the EPA happy. People who can afford a $100k ZR1 Corvette would not give a hang if you told them that 50-weight oil will hurt the car's fuel economy by 2%.