Nothing really. I barely escaped with my testicles over an argument that in really hot climates it was ok to run 20w-50 oil. The thing was I was in the bottom of Arizona and Texas and I also had photos of rod bearings and cams to back up the claims of no damage after 30K miles on that weight oil. In the winter I would run 10w-40.

Right now I run 10w-40 with the turbo most of the year.

Former owner of '99 CSVT - Silver #222/2760 356/334 wHP/TQ at 10psi on pump gas! See My Mods '05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red '06 Mazda5 Touring, 5spd,MTX, Black