OBC TEST No7

[BMW 5 SERIES]

Can you please tell me how accurate is the readings of the OBC when I perform the test No 7 ? This is the test that gives the amount of liters remaining in the tank. I ask this because I want to double check my gas station since I notice a difference of about 2.5 liters from the readings between the OBC and the gas station.

[Paul in NZ]

i doubt very much its will be that accurate.its only based on the fuel level sender in the tank.2.5 liters over a full tank?

[BMW 5 SERIES]

No 2.5 liters over a full tank
The readings at the OBC before refueling was 17.9 liters. I refuel the car with 30euro gas whish means 23.07 liters exactly the liters the pump was showing. When I check the OBC readings again I was expect to see something like 40.97 (17.9+23.07=40.97) but instead of this I saw 38.4liters.
So I m asking this because I want to be sure about the gas station pump

[genphreak]

Can you please tell me how accurate is the readings of the OBC when I perform the test No 7 ? This is the test that gives the amount of liters remaining in the tank. I ask this because I want to double check my gas station since I notice a difference of about 2.5 liters from the readings between the OBC and the gas station.It depends on a bunch of things as the OBC is calculating remaining fuel by taking a bunch of blanaced averages from the float which is bouncing all over the place. There is no way to get empirical about this, the OBC is making a rough guess, sometimes it will be good, sometimes not. It just depends on so many chaotic factors you will never be able to make sense of it. Mine ran out even though the range stated 37km once. Most times it will go to zero and still run for some way before running out.

Understanding this, in normal operation it amazes me how accurate the OBC can be with all the calcs it makes based on fuel levels. :) Nick

[BMW 5 SERIES]

Thanks for your answers. It seems that this not the way to check if the gas station pump is accurate or not so I have to live with the feeling that I get what I pay in my tank.

[Paul in NZ]

the only accurate way i guess is to actually measure ...go to the gas station with a container you know is 20 liters.(Or whatever).