Does running hotter than stock improve MPG?

[cRiPpLe_rOoStEr]

Originally Posted by COcyclist

A hotter thermostat seems to have helped on my diesel Golf. I had struggled to consistently get 55mph on the highway and now I regularly see 60 mpg average at 60 mph.

I guess it might have skyrocketed the NOx emissions. But anyway, With an earlier Volkswagen IDI Diesels, you would be at risk of ruining the engine if you were going for a hotter thermostat.

You don't have to worry about preignition in a diesel. Ignition timing is controlled at the injectors.

Sure preignition won't be a matter of concern in a Diesel, but it should be taken in consideration when it comes to spark-ignition.