Well, this info is a little late if Alster's dealer is correct and can really fix the bug, but I found some interesting things with a little experimentation. I was determined to see if it was a 62 mile bug, a 63 mile bug, a 100 km bug, or whatever.

By timing my last few trips with my trip meter, I've been trying to find the exact point where the reset occurs by ending up in a certain area of town when I near 60 miles on a trip meter. I then repeatedly drive up a steep hill, turn right one block, back down the same steep grade on the next street over, right a block, then repeat. I figured I could catch it happening if I got it on the uphill (getting about 20 mpg) or downhill portion (getting maximum mpg).

I've got the data if anyone wants it, but it was inconclusive. On the first trial I could tell it had reset at 63.4 miles. On the second trial I found it between 63.4 and 63.7, but the data didn't change exactly as expected around 62.2 miles - it seemed stuck on 49.9 mpg longer than it should have (I was on the downhill run at the time, with the instantaneous mpg meter pegged at 100). On the third trial, I detected it at 124.6 miles (divided by 2 = 62.3 miles).

While driving in this circle at one point there was a guy with a long white beard on the corner drinking his lunch from a paper bag. After awhile he started waving to me each time I went by.

It sure appeared that there was another variable involved. So I decided to find out how long it took the meter to reset, as suggested on posts in this forum. What I found was surprising: the time it takes to recover from a manual reset varies - A LOT! After a few tests, I decided I had to try it under different conditions, because it seems to take a lot longer to reset when coasting! Here's roughly what I found:

The quickest it would reset was 4 seconds at 60-65 mph on a flat road (from the time I let my finger off the reset button 'til it started registering mpg). At city speeds the reset time varied from about 6-10 seconds. Long coasts, however, were a different issue. While driving in the city, I once got 37 seconds before it registered mpg. My personal best was a whopping 57 seconds! I accomplished this by decelerating from 46 mph down to 18 mph while coasting, a total almost a mile! It was downhill until about 25 mph when the road inclined back up. I was really surprised. I just kept going and going, and the mpg meter just kept giving me - - - - -. Finally at 18 mph I pretty much had to accellerate or stop dead in the street, so I began to accelerate back up the hill. In about 4-5 seconds it registered the mpg.

So, this variable appears to have a lot of influence on the exact reset point. I'm now leaning towards it being a 100 km bug, that being the point where the reset begins. It apparently could come out of reset and begin measuring again anywhere from 4 seconds to 1 minute or more after the reset begins. But I don't have a way to run a test and control both variables. Maybe a passenger watching the trip mpg closely while going up or down a mountain could tell, but I don't have any mountains nearby.

 

I'm not suprised that you found such differences. It's not really a matter of time. The calculation is delayed until the car has accumulated enough distance AND enough fuel consumption. MPG is miles traveled divided by gallons (ounces) consumed. If you're coasting downhill with the IFG pegged at 100 you're consuming no fuel. So the formula M/G (miles divided by gallons) is dividing by zero. The result is undefined. When you're traveling at 60MPH you accumulate enough distance and enough fuel very quickly. Less so in the city.

There may be a dual threshold, e.g. travel at least 0.1 mile and consume at least 1 ounce of gas, before producing a result.

 

Makes sense, Elan. The max it will display is 150 mpg, of that I'm certain after testing. If it's not there yet, it won't display. Thanks for the explanation.