Ok so I filled my truck up or the first time a few days ago (got the truck not too long ago) and I reset the trip button to calculate miles per tank. I flew through a quarter tank of fuel in 3 days just driving to work and back. A total of 38 miles. I also threw in some diesel kleen in the tank when i filled up. The gauge is exactly at 3/4 full. Now my question.. I have a very bad leak in my first coupler on the hot side of the turbo piping (to the intercooler) and I mean very bad! To the point if you put your finger where the hole is and someone revs the truck, you have to pull your hand away due to the pressure of air coming out.Now will this cause that much of a decrease in fuel mileage?! 5 miles per gallon? That's more than half the milage i should be getting. How?! And I'm always easy on the throttle. Suggestions?