Manila, Philippines

Measure Your Fuel Efficiency: Full Tank to Full Tank Method

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It’s actually simple and easy. I’m no expert here but still just want to share what I’ve gathered so far.
Whether you’re just nerdy, a fan of constant improvement (kaizen) or just plain cost- and emissions-conscious (all of the above for me), it is important to be able to measure your car and your driving style’s fuel efficiency.
Project 366 #32: 010212 Running On Empty by comedy_nose, on Flickr
Some more high-tech vehicles will actually have its own fuel efficiency gauge or even indicators if one is driving economically. But for those with none of these, the more common way is to use the full tank to full tank method. Here’s how:
  1. Gas up full tank at your favorite fuel station, preferably same station, same pump, same octane rating, and if you can, around the same time of the day. Varying day temperatures cause fuel to expand or contract, which affects the volume of fuel pumped inside your vehicle.
  2. Before leaving the station, make sure you record your present mileage or remember it. For example, say 1,500km. Some cars again have the cumulative mileage count (does not reset) and the trip counter which you may reset from time to time. Use whatever is easier for you, the objective later on is to measure how many kilometers you have run.
  3. Go on your normal trips, may it be city driving, highway driving, etc. Preferably, you use the usual route for your daily travels, such as your way to and from work. Factors such as traffic volume and driving speed and travel time will definitely affect the measurement so as much as possible, the driving situations should be similar throughout the measurement. No sudden out of town trips flying at high speeds on the expressway because this will definitely be an outlier, and efficiency in this scenario should be measured separately.
  4. When the time comes that you need to gas up again, have a full tank once more and note two figures: number of liters needed to achieve full tank, and your mileage reading at this second full tank. Again, preferably same pump, same station, around the same time of the day. For example, say 20L and 1,750km.
  5. With these 3 figures, we can now compute the period’s fuel efficiency:
To travel from 1,500km to 1,750km, 20L was used up
To travel 250km, 20L was used up
That’s equal to 12.5km/L
It is full tank to full tank since it provides you the accurate figure on how many liters were used up (via the gas pump), since usual fuel gauges just show needles and bars, and no accurate measurement of how much is left in the tank.Repeat the exercise again and again to see if you are actually improving. Be mindful of exogenous factors that may affect your figures, such as exceptionally heavy traffic, varying routes, or once and a while easy expressway trips.

Compare as well this fuel efficiency with other people driving the same vehicle as you do.

And lastly, be mindful on how you can still improve your efficiency by adjusting your driving style. Shift in lower rpms? Less idling? More cruising? Less heavy foot on the gas pedal?

Photo:  Project 366 #32 010212 Running on Empty by  comedy_nose 

Creative Commons Attribution 2.0 Generic License



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