i have a 2000 1500 4x4 5.3 silverado and i am getting 9-11mpg city and highway. i have a 26gal tank and get around 250-310 miles per tank. i have no idea why i have such bad mpg. i am running 305/70/16 with stock gearing. custom exhaust, CAI, tuneup done in january(fuel filter, CAI install, plugs, wires, oil, oil filter, seafoamed through gas tank and vacuum line.) just changed the TPS. and another thing which i do not know if this is a factor in mpg but my gas gauge doesnt seem to work...the low fuel light is always on when starting and turns off and shows amount of gas after about 5 mins of driving. and when i fill my tank it shows empty even when driving. ive been stumped on this for months and cannot find the solution.