Originally Posted by Dead-On
I fully understand that but the calculations are affected by when I press the reset button. I have to be on relatively flat ground and accelerating at an average speed for it to be relatively correct. If I decide to hit the reset button and let off the gas for just 5 seconds to hit it the average will read high even if my trip is hundreds of miles. It seems to be worse if I hit the accelerator. If I am accelerating when I hit it (even for a few seconds) the average will read about 2-3 MPG lower than the actual usage even if I'm driving hundreds of miles. There's something up with the initial calculation process when you hit the reset button on my JKU .
I'm going to take a stab at this.
You're hitting the "reset" button. That'll reset your MPG to " -- " meaning nothing. It neither represents 0 nor does it represent infinity. So when you hit reset while barley pressing the gas pedal going downhill it'll show a high number. From the moment you hit reset to the moment you look at it, the number that shows is the Jeeps calculated average MPG for that time frame. You are probably achieving 40-60 MPG while going downhill. The same principle applies while accelerating uphill. You are actually achieving around 2-6 MPG.
If you let go of the gas pedal the MPG the computer plugs into the equation is --. So the computer is calculating -- for the distance you have your foot off the gas pedal. In theory you are achieving infinite miles per gallon while you are coasting in gear.
The calculation is a bit different while you coast in neutral. But I don't have specific figures of how much gas the engine uses to keep itself idling.