I am currently running a few saloon racing cars, both NA and TC from 2 to 300 bhp. I was using Castrol 10/60, then changed to Gulf Competition 15/50. I have never had any oil related problems, but I am thinking of moving to a 10/40. All races are about 15 min's long and the climate is Irish, yeh it rains sometimes. I would be grateful for any input.
John