2024 Chevy Duramax Fuel Mileage. But still, my mpg avg is 9.3. I filled up monday with only ¼ tank left and had only gone 340 miles on ¾ tank of fuel in total.

Over the full 1,563 miles, the truck reported 21.3 mpg at an average speed of 68.3 mph—while my math showed about half a mile per gallon less. It’s also likely to improve the big truck’s fuel mileage.