Just wondering if it'll make a big difference with the gas mileage. I turn if OFF most of the time to save my tire's threadlife if I'm just cruising around the city.

I noticed that I'm only getting 19 miles per gallon instead of 21 in city driving. I'm not sure also if my Upsolute chip is responsible for it due to the increased low end torque or the kind of fuel I use which is 93 octane.