I'm guessing that it stores your average over long periods of time unless it gets a hard reset via battery disconnect. I always soft reset my average through the computer after each fill up*, I don't know if this would affect it or not. My guess is that if it's designed well it will record the average MPG value at each soft reset (up to say 10 times or so) and then average that number to arrive at a mile range value. It would be cool if it weighted the "newest" MPG values in its calculation to give you a more accurate range but I doubt it.If there is no past fuel economy information such as after first purchasing your vehicle or the information is deleted when the battery cables are disconnected, the actual distance-to empty/range may differ from the amount indicated.
We've got 13.2 gallon tanks Ralph. So that seems consistent with what I've been getting seeing that you're also in VA with our recent chilly weather. 1.9 gallons left (not 1.4) is about right. You should notice closer to three gallons left once it warms up and we get better mpg's.When I refueled just after the range went to zero, it took 11.3 gallons (going to 3 clicks, e.g. shutoff and 2 clicks more). With a 12.7 gallon tank, that would leave 1.4 gallons. Maybe I didn't fill it. On the Miata forum, a guy claims you need to go to 5 clicks to fill the tank. Suspect that would take it to 1.3 gallons left like it says in the owners' manual (think that's what it says). NOT nearly 2 gallons as you guys are saying.
My experience is that I have 20-30 miles left to go after the readout shows 0 miles left.Sounds like I can cruise quite a while longer below the 1/4 mark with the gas light being the time to look for a fill up but not necessarily be a NOW situation. (As in, gas light comes on, I have a few miles to find a station.)
Note the handbook states "The fuel gauge shows approximately how much fuel is remaining in the tank when the ignition is switched ON. We recommend keeping the tank over 1/4 full." Post 14 says this is to ensure the fuel pump stays cool and to avoid premature failure.And a fun fact. Several members are balsy and hit the trip reset button when the Range hits 0 miles. They've confirm you can drive a good 40 - 50 miles before you actually run out of gas. I normally let my range hit 0 and then fill up. I don't take it much beyond that, but thanks to those members, I don't get nervous when I hit zero, I just know it's time to find a gas station.