Today when pulling a long 6 mile grade up the mountain, the temp rose to 215-218 instead of the usual 204-206. Does the heavier oil (Valvoline MaxLife 10/40) really make that much of a difference???
Yes.There is a difference.
Maxlife 10W40 is 13.94 cSt
at 103*C; and
Maxlife 10W30 is 12.00 cSt
at 95*C, despite being 8*C cooler.
One vote goes to lower operating temperature..... but at reduced oil film thickness ?
Oh no, 10*C higher temperature in 10W40 would half
the oil life of 10W30!!!...... according to experts.
Then OCI 10W40 at 10k and compare against 10W30 OCI at 20k UOA ...... or
OCI 10W40 at 15k against 10W30 at 25k ...... and compare.
Do you need extra thick oil film thickness from 10W40, albeit at higher operating temperatures ?? .........
that's another topic for debate..
Btw,it would be interesting for OP to demonstrate if xW20 operates cooler than 10W30?
Found this figure in lubetech article.Seems like after 30 wt there is very little to gain
Concur with you, in gasoline engine applications ONLY.......
probably not .. in differential gear or hydraulic applications..... vis-a-vis thick vs thin oil comparisons.
Edit: Add info.