I also used to use 15w-50 Mobil 1 trisynth in my TT. I went with the Racing 41 because I drive a lot of short distance stop & go driving which is very hard on oil so i wanted maximum protection for daily driving plus when i let it all hang out at 20+psi I want max protection. I know Gyro and Rob of DSP use just the regular RP 10w-30 in their Z's. I use the RP 10w-30 in my maxima. In both my cars they run smoother, idle better ( idle speed increased on both after putting in the RP oil ). Since it takes my about 1/2 year or longer to drive 2-3k miles I dont change oil very often so cost wasnt a factor...nothing but the best for my baby! I would go with the regular RP 40 weight for a TT in warm weather climate and the 30weight in a cool climate and the Racing oil if highly modded and like to abuse your car now and then.
1990 Twin Turbo 5spd Stillen Stage XI+ "No Show,All GO" 1999 Maxima SE 5spd
ECZA member #0314
..."If it doesnt make it faster, I dont care"...yellowZXTT