Originally Posted by Sahil
Don't rely on the figures you see in your MID. Only way you can figure out for sure is to drive a tankful with AC and then a tankful without AC. On similar roads.
I agree to this, real time fuel consumption reading from the MID is always the momentary one based on the driving style and condition at that time. Tankful to tankful is the best proven method for mileage calculation, I have seen this as the standard chosen by many experts and the one recommended by my trusted MASS Engineer. I would suggest to do this test, no need to finish one full tank but use may be around 5 ltrs and then top up to tank full and record the trip meter readings before and after top up, with and without AC.