Info on fuel efficency??

[Rollingon]

Does anyone have solid data that tells at what RPM and torque (or boost) level the Duramax is most fuel efficient - that is, it consumes the least fuel for the power produced. A BSFC curve would be great, but any good info would be appreciated.

[Kennedy]

I think you will find that 55-60mph is about the best. Wind is a major factor here. Those seeing the best mpg seem to be running at a more moderate pace...

[Jim Brzozowski]

Stock, I've found 1800rpm to be the most efficient. With the juice?