Fleets that have selected Diesel as their primary fuel may have done so for proper reasons more than 10 years ago. Gasoline engines could not perform anywhere near their diesel alternatives. Diesel fuel was more inexpensive than the only other alternative, gasoline. The upfront premium for the diesel option was offset by better resale value. Maintenance costs were lower due to longer service intervals, and vehicle engine life was significantly longer. But times and conditions have changed.