In my 2016 Discovery Sport HSE the cars estimate consistently indicates 10% better efficiency that paper and pencil. True miles per gallon runs 28 highway, 24 city. Your mileage may vary.Recently made a 7 hour trip. 4 people fully loaded. Highway was 27 MPG. Petrol version. How does that compare to anyone else?
Last fall I checked my speedometer using my garmin GPS as a reference, set my cruise to 100KPH on a long flat stretch of road and the GPS showed a constant 99KPH so 1% error. No measured distances on the road but odometer appears to be in my favour.I gave up on manually calculating it a few years ago, when I realized most speedometers and hence odometers are usually at least 5% off too. Weird that they almost always read fast which makes your mileage seem better and your warranty run out faster. So even manual calculations have some inaccuracy and they're only really useful for relative measurements, which your computer does about as well.