Is Accumulated Milage Indicator Accurate? (MID fuel economy / MPG gauge)

[nternal1]

I just filled up my first tank of gas and found that, while "accumulated (total) milage indicator B" claimed 13.8 km/litre, my own calculation (based on the gas I actually put in the tank) put it at closer to 11.4 km/litre. Being new to the car I may have inadvertently reset the trip meter but... I doubt it. The next fill up will tell me if the displayed milage indicator can be trusted but I really don't want to wait four weeks to find out. Does anyone else have an opinion on the accuracy and trustworthiness of "accumulated milage indicator B"?

Ps My trips are generally very short (7 km or less of city driving) and I realize that "fuel consumption indicator A" (the one that only gives the milage per trip) is not going to be very accurate. It is "total milage indicator B" that I am wondering about.

[fifteenwindow]

The fuel economy numbers that my mirage shows at the end of each tank have consistently been higher than my actual fuel economy (trip odometer mileage divided by gallons pumped at the gas station). I have noted what fuel economy my car has displayed at each fill up in my fuel log.

[MetroMPG]

Fifteen - have you figured out a % error?

The 5-speed Mirage I had for 2 weeks was accurate within about 4% of calculated-at-the-pump mileage over 3 fill-ups. Mostly highway driving.

I was actually pretty impressed by it.

[MiMi]

I agree with MetroMPG. After nearly 40 fill-ups, the fuel consumption indicator B is 2 - 4% lower (l/100 km) than the actual calculated consumption.

[nternal1]

I agree with MetroMPG. After nearly 40 fill-ups, the fuel consumption indicator B is 2 - 4% lower (l/100 km) than the actual calculated consumption.

I would consider that reasonable and within the tolerances one might expect in a "measuring" device but...
I got 18% lower in my first tank than indicated by the accumulated milage display. That seems absurdly far off. I guess I'm going to have to wait for my next fill up to see if the error was mine.

[thumper]

The fuel economy numbers that my mirage shows at the end of each tank have consistently been higher than my actual fuel economy (trip odometer mileage divided by gallons pumped at the gas station). I have noted what fuel economy my car has displayed at each fill up in my fuel log.

I've noticed this same. My formula (avg mpg - 5) = real mpg.

[nternal1]

God****it, it pisses me off that I trusted those morons at NRCAN to have accurate "relative" fuel econony information. I got the CVT thinking I was getting an ultra fuel efficient car and now I'm stuck with a piece of junk (that I paid extra for) that doesn't even remotely come close to what I expected (even after modifiying my driving technique and driving like a little old lady). It just adds insult to injury that I watch the "milage" indicator like a hawk only to find out it also can't be trusted.

[IchabodCrane]

You don't know exactly how full the first tank of gas was from the dealer so just because you put say, 29L in at your first fill doesn't mean you used 29L of fuel.
The accumulated mileage becomes more and more accurate over time as it is then averaged over many more fillups

[m4v3r1ck]

7 km travel in the city ... better take a bike. Cheaper, gets your body moving, better for your cardiovascular, better condition, saves money on gym .... and ... (just love to say it) save the environtment

[nternal1]

You don't know exactly how full the first tank of gas was from the dealer so just because you put say, 29L in at your first fill doesn't mean you used 29L of fuel.
The accumulated mileage becomes more and more accurate over time as it is then averaged over many more fillups

I filled up first before resetting the mileage indicator. My comments are based on the next fill up that came after that.