Originally Posted by Stagman
I have had my truck just under 3 months and now have 7800 miles. I'm getting between 17.5 and 16.5, manually calculated, overall with 80% being interstate at 70 MPH. Before it cooled off those numbers were almost 1 mpg higher and I've always had the same results of lower MPG in cooler weather on other vehicles as well. I had something interesting occur on my last fill up. EVIC was saying 15.1 average mpg which is the lowest I had observed and I attributed it to headwinds all week long, swear it changed midday
. However when I filled up it calculated out to 16.8. Usually it would show higher, calc lower. Just found that interesting.
I have the fancier computer data readout deal like the EVIC on my GM vehicles, but that fuel mileage calculation component can be off as much as 2 mpg or more. I always do the true mileage to fuel used for figuring mpg, as it's much more accurate. The trip and permanent odometers always seem to be right on the money by mileage sign checks and GPS comparison.