Tripmeter is other than the main meter. It is adjustable to zero as & when you want. It is mainly useful for 2 purposes (1) to measure the no. of kms travelled on a particular trip, say when you are taking a trip from Mumbai to Pune & back, you set it to 0 at the time of starting your trip. When you are back from the trip you know how many kms you have travelled on the particular trip. It saves you from remembering/calculating the kms travelled from the main meter; and (2) to calculate the mileage of the car, i.e. you set it to 0 at the time of filling tank full with fuel and then set it back on zero at the subsequent filling (tank full). You then divide the no. of kms travelled (as per tripmeter) by the no. of litres of fuel filled between the two tank fulls. This will give you the mileage.
