Here are the instructions for calibrating the On Board Computer in your Z3 to obtain accurate MPG readings.
To get the new correction factor you will have to first Brim the tank, reset the OBC so you get a clean MPG estimate for the tank and run it to empty then brim it back up and calculate your actual mpg using the formula below;
litres of fuel to brim tank divided by 4.546 = Gallons
Number of miles on a tank divided by above gallons of fuel = Actual MPG
Once you have your actual MPG also take the reading from the OBC for the estimated MPG then you will be able to use the following formula to calculate the new correction factor and pull the OBC MPG reading somewhere nearer to the real MPG.
New correction factor (CF) = Old CF x (actual MPG/OBC MPG)
Just use the above instructions in the picture to input the new CF on the OBC.
And Bobs your uncle
To get the new correction factor you will have to first Brim the tank, reset the OBC so you get a clean MPG estimate for the tank and run it to empty then brim it back up and calculate your actual mpg using the formula below;
litres of fuel to brim tank divided by 4.546 = Gallons
Number of miles on a tank divided by above gallons of fuel = Actual MPG
Once you have your actual MPG also take the reading from the OBC for the estimated MPG then you will be able to use the following formula to calculate the new correction factor and pull the OBC MPG reading somewhere nearer to the real MPG.
New correction factor (CF) = Old CF x (actual MPG/OBC MPG)
Just use the above instructions in the picture to input the new CF on the OBC.
And Bobs your uncle
