Yeah, I totally don't agree with either of you.

15w40 would not be too thick or hurt the oil pump for sure.
Maybe if you were running like SAE50 or 60 you might fry the cams and suck up some serious power, but thats about it.

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