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Horrible fuel mileage please help

Skylardog123

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Skylardog123 Enthusiast

Skylardog123

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I know this topic has been beat to death, having to move soon and with the gas mileage I'm getting, I might have to sell the truck,  so I have a 99 silverado 1500 4x4, with a 5.3, getting 9.5mpg, it has a custom tune on it, new o2 sensors, cleaned maf sensor. New plugs,  fuel filter,  full synthetic fluids all the way around, swapped to electric fans, ran seafoam in it countless times, clean throttle body, no dragging brakes, I've rebuilt the entire front suspension, new u joints, 3.73 gears, 34 inch tires, havent seen any vacuum leaks, fuel trims are within spec, compression is perfect, fuel pressure is good, I'd be fine with 12-13 mpg, but even when I had stock wheels and tires with a tune. I still only got 9.5 mpg now I have 34s with a tune and oddly enough. Still gets the same mileage, what can I do to bring it up a little bit, its killing my wallet, i see all these other guys on 6 inch lifts getting 15mpg and i cant even break double digits

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