LANCER wrote on 01/08/18 at 15:59:32:In a multi weight oil, the oil should not thicken until higher operating temps are reached. OR ... does our engine normally operate at those higher temps routinely ?
This is a trick question (and dave is right)
But lets consider
normal operating engine temp only.
40wt oil is 40wt and 50wt oil is 50wt... whatever the viscosity is.
40wt will slip thru the orifices faster than 50wt.
At freeway speed you have 50psi, and whatever flow that might be.
It goes to the top of the head and out the cam journals... for the most part.
Thicker at this point will mean less flow, less heat carried away.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1283117891/0