How accurate is the MPG indicator.??

[Jeff15]

Does this give an accurate average or is it just for show?

[peteo48]

I can't speak for the Mk4 but my Mk2 and my current Mk3 both overestimated mpg by about 4 mpg on average. It would vary a bit from tank to tank but not by much.

[ColinB]

Does this give an accurate average or is it just for show?

Depends what you mean by “accurate” and why you want that accuracy. If you’re keen on measuring your mpg with decimal places, then it’s not that accurate and you need to do something else. But if you just want to ensure you’re driving as efficiently as possible (which is actually why it’s there), and be able to take action if your mpg starts dropping off, then it’s plenty accurate enough.

[Jeff15]

Just a ballpark figure would do..

[Jazzik]

You want accurate MPG? Use (for example) this: https://www.spritmonitor.de/en/

Easy:
Use Spritmonitor.de on the road with your Android- or Apple-smartphone and the Spritmonitor.de app! Enter new fuelings right at the gas station.

[Worthingmike]

My warning light came on and about 4 miles later i filled up. I got 35.3 lt in. So i think the warning light is just over 5 lt left.

[Worthingmike]

Sorry i have posted this in the wrong post. It should have been in the fuel post. Geting old.

[ColinB]

You want accurate MPG? Use (for example) this: https://www.spritmonitor.de/en/

Easy:
Use Spritmonitor.de on the road with your Android- or Apple-smartphone and the Spritmonitor.de app! Enter new fuelings right at the gas station.

Spritmonitor is just a calculation tool, the accuracy of the results depends on the accuracy of the data you enter. Sources of error can be the accuracy of measuring the fuel added (eg brimming the filler pipe in exactly the same way every time), and that the odometer reading can be a few % out.

[Expatman]

You want accurate MPG? Use (for example) this: https://www.spritmonitor.de/en/

Easy:
Use Spritmonitor.de on the road with your Android- or Apple-smartphone and the Spritmonitor.de app! Enter new fuelings right at the gas station.

Spritmonitor is just a calculation tool, the accuracy of the results depends on the accuracy of the data you enter. Sources of error can be the accuracy of measuring the fuel added (eg brimming the filler pipe in exactly the same way every time), and that the odometer reading can be a few % out.

Sure, but if you run the calculation over several fill-ups then the vagaries will be ironed out and the overall average will be very close to real consumption. Certainly accurate for comparison purposes.

[ColinB]

Sure, but if you run the calculation over several fill-ups then the vagaries will be ironed out and the overall average will be very close to real consumption.

Only if the errors are broadly above and below a mean value over repeated fill-ups. If they are biased to one side of the mean (eg if the odometer error is due to tyre wear) then you'll get a biased result.

Certainly accurate for comparison purposes.

But so is the car's computer read-out!

[Downsizer]

Just a ballpark figure would do..

Over 46000 miles in my Mk3 with trip B left running throughout, I have found the display to be about 9% optimistic showing 56.8 mpg while the true figure based on fuel bought is around 52. I expect the Mk 4 computer will be similar.

[John Ratsey]

I also found the Mk. 3 to be about 9% optimistic (I have to wonder if Honda wanted people to think it was significantly more frugal than the Mk. 2). I'm seeing about 5% optimism on the Mk. 4.

[Expatman]

Sure, but if you run the calculation over several fill-ups then the vagaries will be ironed out and the overall average will be very close to real consumption.

Only if the errors are broadly above and below a mean value over repeated fill-ups. If they are biased to one side of the mean (eg if the odometer error is due to tyre wear) then you'll get a biased result.

Certainly accurate for comparison purposes.

But so is the car's computer read-out!

Not if you are comparing between 2 different makes of cars.

[peteo48]

Just a ballpark figure would do..

Over 46000 miles in my Mk3 with trip B left running throughout, I have found the display to be about 9% optimistic showing 56.8 mpg while the true figure based on fuel bought is around 52. I expect the Mk 4 computer will be similar.

Pretty much my experience over the Mk2 and the Mk3. Although I do brim to brim measurements myself, I think you can work with the figures given by the car's computer by just making an adjustment. If I knock 4 mpg off most my computer readouts I am pretty close to the actual consumption. I do the trip B thing as well.

[guest4871]

Why is there a consistent variation?