Have 31's on my 2001 Sport Trac here in San Diego (low elevation), and the best it gets is 14.5 mpg average. I have a UltraGauge plugged into the OBD2 and it gives me real time mpg along with average. I'm always pretty light on the gas pedal. Is there something wrong with my truck if it's only averaging 14.5?
Has 85k miles, a K&N filter that I keep clean, stock air box snorkel removed, but have yet to replace the spark plugs/wires, and the exhaust cats have never been replaced...if that has anything to do with it.