Switched to 5W-40 synthetic in my fleet, mileage went up 2 mpg

I got tired of fighting cold start knock on my 6.7s so I broke down and tried the fancy oil for a few months. After 3 oil changes across 4 trucks in Phoenix, the average fuel economy went from 15.8 to 17.9 mpg, plus the oil analysis came back with way less wear metals. Anyone else run full synthetic year round or is that just throwing money at the problem?

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river_hart182mo ago

Man, that oil analysis saying less wear metals makes the extra cost totally worth it to me.

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