Isx15 horrible mpg

Driver Tested We ran one of our new trucks with the PACCAR MX-13 to California and back twice, and the driver averaged 9.1 miles per gallon. Just unbelievable.

 

The trip began in Scottsdale, Arizona and ended 1,028 miles later at the Peterbilt factory in Denton, Texas.
Denton took my numbers down even further until the trip average read only 10.2 when I turned off the key.
When I saw the numbers creeping up into the 10s on a recent test drive in a Peterbilt 579 EPIQ,

 

Funny thing is, I drive the hell outta this truck!

It's a Cummins. Cummins are meant to work. They don't tolerate being babied and cosseted like a Detroit. Feed'em and Beat'em! Maintain the maintenance, and run'em hard. They will burn cleaner and run smoother that way.

 

You have had yours what 3 months???

 

14,000 miles.

And I've done some work to it. Realignment, 2 oil changes (switched it over to full synthetic), new driver tires, reprogrammed the auto transmission shift points to work better with the engine, reset the valve adjustments, cleaned the engine top and bottom (Power Service is GREAT STUFF!), Biocided the tanks, dumped and changed the fluids (radiator, transmission, both rears. Oh, and I changed the engine air filter.

I like to keep ahead of my maintenance, as you can see.