OVERKILL
$100 Site Donor 2021
I never said it was too thick, but a 40 will be thicker than a 30 at temp, no? The maker of the engine perhaps says 40 is too thick by specifying use of a 20 with a 30 being "ok". Since 40 is not mentioned by the manual then perhaps they don't mention it for a reason?
Dude, you literally stated:
Jimmy_Russels said:Won't the 40 be too thick
The fact it was a question doesn't change the fact that it was a proposition of possibility to which I answered.
A xW-40 will be slightly heavier at temp than an xW-30, but both will be massively thinner than they were at startup. The maker will have determined the minimum level of viscosity necessary to keep parts separated and things together until well beyond the warranty period in testing and have made that the spec. This allows them to get the best possible CAFE credit, which is one of the main drivers towards thinner and thinner oils as even a small fraction of a MPG gain over millions of vehicles is extremely significant.