2009 GMC Sierra HD 3500 6.6L diesel MPG

How do I find out information on the actual MPG that owners are getting?

So far, GM has only sold 6 of them so there are few owners to answer your question…

The EPA hasn’t tested it yet. You are out of luck.

does the EPA even test diesel fuel mileage?

Yes. They have data on the VW and MB diesels available this year.

Thanks for the info. I know that there is nothing from the EPA or GM but I was hoping to hear from someone that owns one. Didn’t know that there were that few sold.

Yes, but not for 250/2500 and larger trucks.

The EPA does not test any vehicle with a GVW over 8500# since fuel economy rules do not apply to heavy duty vehicles. That’s why you will see the Ford F150 but not the F250 or F350. They have to draw the line somewhere so that true commercial vehicles don’t count against the CAFE ratings.

The OP is considering buying a large pickup, but is concerned over fuel mileage? Anyway, word on the street is that the Duramax gets around 13-16 MPG overall. Right now it makes more financial sense to go with a the biggest gas engine they offer. Fuel mileage will be a bit less, but you’re also not spending the extra $7500 premium for the diesel and you’re paying less for the fuel itself.