Originally Posted by elp_jc
M1 5/30 in TX here. 5/20 is recommended by manufacturers so they can get a fractionally higher CAFE standard, not because it's better for the engine, especially in hot climates. Alaska is not the same as TX. Even with our super mild winters I can leave my hand on top of my engine in winter without burning myself. Try that in summer
. It's simple common sense engines run a lot hotter in summer. Remember your coolant temperature gauge doesn't move from 190 to 235º (fans kick in around 225º), but just as engine is cooler to the touch than 190 in winter, it's hotter than 225 in summer. Either grade is perfectly fine at any temprerature, but I'd use 5/20 if I lived up north.
By the way, the K24 engine is identical than in 2002, when manual recommended up to 10/40 for hot climates. Blame the EPA for 5/20. Good day.
I agree. If you want genuine protection from high oil temperatures and oil shearing, 5W-30 is the only rational choice. Which is precisely why Honda never changed its recommended oil viscosity for the higher performance k-series engines.