Hello guys Ive got an 07 LBZ 2500 4x4 totally stock. While towing a 10,000 lb load I normally get 10-12mpg depending on speed etc. On my last couple trips I'm only getting 5-7mpg. Right before this occurred I changed the fuel filter but cant see why that would cause the increase in mileage. Also have cleaned the MAF sensor and changed the air filter. When not towing the truck gets 17-18 on the highway and about 13-14 around town. Any ideas guys?