Miles to refuel gone wild?!

The miles to refuel on trip computer used to be quite accurate. If it says 200 miles to refuel, I should probably drive close to that number.

But today, I just realized on a 20 miles trip, the miles to refuel dropped almost 60. When I start paying attention to the number, it seems to drop two miles for every miles I drive. In the city, it drops by 1 like very 2-3 blocks or 2-3 minutes. But average MPG in the computer did not change while all these were happening. I wasn't keep track of actual MPG, so don't know the real number.

The only problem I had before this is a 15 seconds AWD malfunction warning that went away almost immediately. Someone on the board mentioned this could be related to dying battery. It's a 3 years old car with 16K miles, so that's a possibility.

Any clue what's going on? I want gather some info before going to the dealer so that I won't get robbed under warranty, again!

Well, this is perfectly normal. 2 things you need to remember:
1) Miles before empty is based on calculated MPG and current speed - which varies when you hit traffic, sit at lights, etc
2) MPG is cumulative, not instant, so it is calculated from the last time it was reset not your current MPG.

Thanks. Shouldn't miles before empty calculated based on MPG and remaining gas? For example, if I drive 45MPH vs 65MPH, which both in the optimum MPG zone, shouldn't miles remaining pretty much the same?

I noticed that the number dropped from 265 to 200 on a 16 miles highway drive at 60-70MPH. Then the next 4 miles or so local drive, it dropped below 180. That's way off from what I remembered.

So you think I should track a few more tankful of gas before going to dealer for check up?

Originally Posted by pjinca

Well, this is perfectly normal. 2 things you need to remember:
1) Miles before empty is based on calculated MPG and current speed - which varies when you hit traffic, sit at lights, etc
2) MPG is cumulative, not instant, so it is calculated from the last time it was reset not your current MPG.

actually sounds like every bmw I have ever owned. To me the DTE gauge is more of a ballpark than true. I track my fuel by trip odometer and "fuelie" style app. Much more accurate. But then again, both my rides are as thirsty as a sailor on furlough

Originally Posted by pjinca

Well, this is perfectly normal. 2 things you need to remember:
1) Miles before empty is based on calculated MPG and current speed - which varies when you hit traffic, sit at lights, etc
2) MPG is cumulative, not instant, so it is calculated from the last time it was reset not your current MPG.

1) It uses an average MPG (although I'm not sure over what time frame it builds that average. i.e. whether it's last 20 miles or last 5,000), but either way, it doesnt't vary hugely just by sitting in some traffic. Unless maybe you're in LA traffic, lol

Mine does this all the time--you have to remember that the difference the fuel level sensor sees from say 9 gallons of gas to 8.5 gallons left is small to say the least. It's not unusual for it to move around a little bit from hills, splashing around, etc.. Obviously car manufacturers try to minimize that, but I see it pretty often. Especially if I park on a hill or anything like that