False mileage by on board mileage calculator

[dms664]

So guys i topped up fuel tank of my gli 2010 n traveled 600km highway travel. The on-board mileage calculator was showing average of 12.7 km/l. On culmination of journey i topped up the tank again n it got filled with 40 litres.
600km in 40 litres gives average of 15.
My query is why there is so much variation between the actual mileage n the one given by on board computer. Can we do something to improve its accuracy? Needless to say that I reset trip meter, average n time elapsed meter before start of travel.

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[biloo]

Did you reset the meter before setting off ?

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[hussaialy]

How you validated the accuracy of pump meter?

[rajaatta]

So guys i topped up fuel tank of my gli 2010 n traveled 600km highway travel. The on-board mileage calculator was showing average of 12.7 km/l. On culmination of journey i topped up the tank again n it got filled with 40 litres.
600km in 40 litres gives average of 15.
My query is why there is so much variation between the actual mileage n the one given by on board computer. Can we do something to improve its accuracy? Needless to say that I reset trip meter, average n time elapsed meter before start of travel.

Sent from my GT-I9500 using Tapatalk

Before refilling from the firt station just reset the milage economy meter and on next refill you will find the actual milage. If some how you forgot to reset the mileage economy meter and keeps on driving until your next refill you will find huge variation in the figures. So always reset the eco meter on refill.

[haseeb.basharat]

There are two gauges.
One of them will show you the current mileage you're getting per liter and the other one will show you the overall mileage you have. I think you're looking at the one with overall mileage. It will not change. It tells you the average since day one to now.
If you want to check it for long routes than just unplug the positive terminal of battery, and the computer will reset and mileage will get zero. Now, it will recalculate the average.