O.W. Kenobi

I have noticed that my mileage left until empty display fluctuates dramatically once the indicated miles drop below 100 until empty. Often, I am expecting 300+ miles on a tank, only to have it go to zero well before 260. If I fill up at that moment, there's still 1.5 to 2 gallons left in the tank (only taking 14 to 14.5 gallons of new gas). I thought about watching the gas guage, but that seems tied to the mileage left display (fluctuates also). What gives? I'd like to be able to judge my tank a little better, but that computer seems pretty off. I have tried minimizing the changes in my driving habits for 3 tanks now, so I'm conscious of not stomping on the gas for a quick pass (just doing this until I figure out the gas situation) or running the AC too much. Any thoughts? This car is an '01 with about 1500 miles on it, if that helps.

StealthMobile

Assume 4 gallons in the tank. If you are cruising at 70MPH and getting 25 MPG, the computer will say the range is about 100 miles. Then you turn onto a city street with stoplights/stopsigns. If you "use the boost" (force?) and only average 15MPG over the next few miles the computer will have no choice but to tell you that your range is now less than 60 miles. The miles-to-empty is based on the average MPG of the last few minutes of driving time.

O.W. Kenobi

My speed varies over the entire tank (obviously), but the miles left until empty seem to steadily decrease until I get under 100 left. Then, it drops in much more significant chunks, sometimes 10-20 miles in only a few minutes. That doesn't happen when there's more gas in the tank.