My 2003 F-250 is just drinking the diesel. I do good and get about 15 mpg then all of a sudden it drops to 10-12. This is while I'm hauling campers. It's done it twice now. What is going on? My truck has new injectiors and the trans was done awhile ago. I have 330,000 on her, but I don't beat on her. Any ideas? I'm stumped. I clean out the air filter, and ran diesel cleaner through. It ran fine and it started again last night. It happens when I'm hauling through Nebraska and Wyoming. The hills are just killing me. I'd appreciate any ideas.