How do I calculate the mileage in my car?

What’s the right method to measure fuel economy in your car?

Going by the average fuel economy reading displayed in your car’s instrument cluster is not the right way. Noting the needle position when you fill fuel, and measuring how far the car travelled until the needle ‘got back there’ is also not the right way. Resetting the trip meter when the low fuel lamp begins lighting up, and checking how far the car travels until the lamp starts glowing again is also not the right way! So then what’s the right method to accurately measure fuel economy? Let’s help you get this right! Here are the steps:

  1. Go to your neighborhood trusted fuel station.
  2. Ask for a full tank, and stop fueling when the pump does an ‘auto stop’. Don’t fill any more fuel, once the pump cuts off automatically.
  3. Reset the trip meter.
  4. Drive 50 to 100 kms on the highway, preferably early in the morning.
  5. Come back to the same fuel station, and if possible, the same fuel nozzle (optional).
  6. Repeat step 2. Remember to stop fueling when the pump automatically stops.
  7. How many liters of fuel did you fill? Note down the exact reading in the fuel pump. Let’s say it was 4.85 liters.
  8. Next, check your trip meter reading. How many kilometers did you do? Let’s say the trip meter shows 63 kms.
  9. Your highway fuel economy is 63 kms / 4.85 liters  = 12.989 km/liter, which is approximately 13 km/liter.
  10. If you want to know your fuel economy in city conditions, repeat the same steps in the city. That’s it!

Keep in mind that fuel economy varies wildly with traffic conditions, aggressive or defensive driving habits, usage of A/C, tyre pressure, number of time brakes are applied (converting kinetic energy back to heat), maintenance of your engine, and many other factors. Also keep in mind that unlike cars of yester years, there is no more ‘tuning’ done during car servicing! That’s now taken care electronically by the ECU (Engine Control Unit). The ECU relies on clean air and fuel filters, good quality engine oil, sensors and actuators in good working condition, and a few other things to keep things going well. The software takes care of all the decision making – there’s no more tuning involved.

Our experience shows that many owners panic after seeing the fuel economy readings on their instrument clusters. One proper measurement, and the heart beats are back to normal. Happy measuring!