MPG gauge accuracy

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The mpg gauge on my Scion Xb (2014) reads 7% optimistic. My Scion Xd ( 2103) reads 4% optimistic.
 
Only sure is to mathmatically calculate and average the results.
 
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Originally Posted By: horse123
Hand calc is significantly less accurate than the MPG readout in most cars. Pumps shut off at different times, different gas blends foam slightly differently and cause different shut off times as well.


At the time of first fill up both cars had low fuel light on. I always top off until I can see the gas in the filler neck. So pump-shut-off is not an issue.
 
If any, the old 3-series is a tad conservative with the instant readout on the cluster, particularly if the A/C is on, the cycling generally swings the gauge by about 1L/100km.

On a long trip, A/C on, it has read 8.5L/100km (27.6mpg), but the actual average for the three fills en-route was about 7.4L/100km (31.8mpg).

The fuel gauge on the car marks each 1/4 of a tank with litres. Basically, so long as I'm doing at least as many KM as I use litres of fuel (by the gauge), I know my average is good! The markings on the gauge ARE accurate. If the gauge is 1/2 (30L), and you add 30L, you get 60L. Capacity is 65L, but it usually cuts off before that.
 
My old Jetta could be very consistantly filled up. Fill until pump shutoff, then pull the nozzle out and keep pumping until no more could fit. Very repeatable.
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My Mini Cooper is always way off. I can't trust the gas gauge either. The computer usually says an avg of 40-44 mpg and I track my consumption on all my vehicles with an app (gas manager) so don't even consider individual fillups. The Mini is 38.4 over the past 20k or so, My Dodge 2500 Cummins with 192k on the clock has avg'd 20.5, the Mercedes ML320 avg 20.4, and my Motorhome 8.2 mpg. None of them have a computer readout that is anywhere near close. All really high side optimistic
 
Originally Posted By: horse123
Hand calc is significantly less accurate than the MPG readout in most cars. Pumps shut off at different times, different gas blends foam slightly differently and cause different shut off times as well.


Originally Posted By: ARCOgraphite


How did you like the sentra driving experience. BMW 3 series like?


LOL THAT'S FREAKING HILARIOUS. GOOD JOKE BUDDY.
Not joking. the last sentra I drove was better than the last 3 series I drove (318ti) - except for the engine.

STD beemers aint all that. My 96 Contour V6 5m would trounce them in the day for comfort speed and agility.

That why drug dealers buy Beemers, you have to be on drugs to pay THAT much for meeh performance.

That said I thought my 98 M roadster was the best sports car Id driven next to a 300ZX. This includes Porsche Carrera 4, 911's, Porsche 944 ( nice driver there actually - add that to the above 2 top performers) The Honda S2000 just didn't gel.
 
The mpg readout in my Buick Park Avenue was always 10% too high, and the gallons used about 10% too low. I learned to compensate when wondering how much money to give the clerk. If the readout said 10 gallons used, I'd presume it would need 11, and give him (in those days of 3.00 gas) $40, and get ~$7.00 in change.

The readout in my Buick Regal with the 2.4L engine is sometimes high, sometimes low, sometimes almost exact. I use my Exxon credit card now, since I get .06/gallon off, and don't need to wonder how much cash to post up front. Besides, the Regal doesn't have a "gallons used" readout.
 
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