Anyone else have issue with the mileage on the trip computer being off? Mine usually is off 3 miles per gallon.

My 2010 overstated my mpg by 5.5%. My 2014 overstates it by 5.0%. The speedometers also overstate the mph. The odometer is reasonably accurate provided you don't change the diameter of the tires.

Mine appears to show an MPG estimate of about +/- 2%, which is more accurate than most cars I've owned (which is a lot). Nevertheless, calculated [odometer vs. gallons] is the only realistic way to get solid long-term data.

The OBDII knows the actual speed, it's just that the computer displays a lower speed. E.G. OBDII and GPS will say 71 MPH but the speedometer will display 73 MPH. That's a better displayed accuracy than previous gen MINI's. If you need actual speed, use a GPS or a ScanGauge.

It always needs mentioning that there is a built in (on purpose) +2 to +3 MPH difference between indicated and actual speed mandated by the EU.

Thanks - I hadn't seen that before. European regulation ECE-R 39 says 0 ≤ (V1 – V2) ≤ 0,1 V2 + 4 km/h.

Funny - several Mercedes that I've driven have pretty much exactly matched the speed shown on an auxiliary GPS. I've no experience with a BMW, but my 2015 F55 speed reads high by a solid 4mph at 70. When I asked the service manager he said they all do it. I find it annoying - oh well, 1st world problem.

exactly,its allowed to be spot-on, just not low. All having nothing to do with the thread topic...

Another 'hate to bring it up' issue here. The MPH discrepancy between GPS and indicated speed has been a common topic in a multitude of threads. A little searching would have uncovered all this. Of course the thread participant that points this out often has fruit, vegetables and worse thrown at him for his efforts.

Mine seems to vary depending on how much highway driving I've done. I've only filled up three times. The first was spot on. The second time was off by about 3 mpg. The third fill up was very close(within 1 mpg). The first and third tanks were about two-thirds highway driving, and none on the second tank. Seems like it may be underestimating fuel use driving around town (or at least mine does).

The MPG on my 2007 was spot on. On my 2014 JCW it says I get about 2 MPG better than I really do.

My 2014 3s trip computer averages 3 miles better than I really get. Last fill up was dead on. The speedo is exactly 5 off. Guess that will help with tickets.

Am I the only one catching this error? My MCS is running right about 35 mpg or 1/35 gpm. The above would mean either running negative gpm (-2.65 gpm) or 3 1/35 gpm. In mpg that would be pretty low (less than .3 mpg fuel use). I hope what was meant was off by 3 mpg which is about a 10% error.

Actually have a very important comment to make.

I've had my F56 MCS for a month now. I noticed my car uses UK gallons in MPG calculations and has no setting to switch to US gallons. This is very deceiving. I was blown away by my 45+ MPG highway runs...until I realized it was only mid 30s.

Anyone else notice this?

good catch, no I don't drive and M1A2 Abrams. I changed to 3 miles per gallon.

There is a setting in the computer to change units. Try searching in the onboard owners manual. If you can't find it, your dealership can help fix the setting.

I've found where to switch units but the only options are km/l, l/100km and MPG. MPG, in this case, is UK gallons. It's possible the car is programmed for the wrong country (UK) but my sidemarkers light up and I don't think they would if it was programmed for UK. I just run it in L/100km now anyway.

Ok. I have an idea. Is the system language set for English (UK)? If so, that might automatically change the gallon unit without it explicitly stating.