I heard an interesting thing from my cousin. My uncle (his dad) is currently stationed in Afghanistan. One of the mechanics told him to mix 2 quarts of ATF per tank into their HUMVEES (which use a lightly modified Duramax diesel). He claims this improves engine economy and performance. My cousin then mixed in ATF into the fuel of his 1991 F350 7.3 Diesel. Before, he had added a garret turbo and bigger Bosche injectors, so the engine smoked and rumbled quite a bit. My cousin has noticed economy has improved to 19MPG (where it was 16 before), the motor doesn't rumble nearly as much, and their is no noticeable smoke. I can tell you first hand that motor smoked and rumbled quite a bit at idle. I cannot know if this will work on a more modern civilian motor with emissions standards as stringent as they are, but it is worth a shot. My cousin claims the Fuel/ATF level should not exceed 3/1, or 1 quart per tank.