yesterday I got 700.9 miles out of a single tank of fuel. This is a personal record for my van. I used 23.619 gallon for 29.7 mpg. The van is a 2014 Promaster 159" 2500 with a 3.0 liter diesel. I fill up in Gulfport MS went to Memphis TN and then to Athens TN. I was using Chevron fuel. I think I get better mileage on that brand. I had cruise control set at 58 mph and there was very little wind.