Im just wondering about what kinda gas mile i should be getting. I just got this truck its a extended cab 1998 gmc z71 k1500 with the 14 bolt. and im averaging like 10 to 11 likes to the gallon. 5.8 gallons get me about 45-60 miles depend on driving style. the only thing different from stock is that it has 285 ATs on it. And i just put new fuel filter, spark plug, and wires.