My nieghbor drag races a 67 vette. 580 CID. $30,000 for the engine alone. Slicks,wheely bars ect. 2000 HP with 2 stages of NOS. Best time in 1/4 is 7.55. Since day one his racing team has used 5w-30 Synpower. This oil was recommended by the engine builder. He has raced this car for 3 yrs. with several races a yr. Has anyone heard of not using a racing oil under these conditions. And he has never had a problem with the engine.