I've switched from 20W-50 Valvoline to Castrol 10W-40 in two different cars now, and both picked up 8-10 psi of oil pressure across the board, both cold & warm. I have two friends who had told me they experienced this very same deal when switching to Castrol in their vehicles. I told them they were full of, well, you know, and figured I'd try it for myself. I ate my words on that one.
Anybody have any ideas why this happened? Also, the Castrol seems to be much cleaner compared to the Valvoline when I change the oil. More detergents, maybe?
