A great tool to help with the process of Ecodriving and ultimately with fleet fuel savings is real time and driver accessible metrics.  Metrics that include average and instantaneous fuel economy gauges.

A common question we get at Ecodriving Solutions is to explain the difference between the two values and why they are so different from one another at various times.

Instantaneous fuel economy is the number in miles per gallon that you are getting from the vehicle at any given time. It is likely to change radically depending on what you are doing with the vehicle at that particular point.

For example, it should be obvious that when you are at a standstill idling, your  miles per gallon value on an instantaneous readout will be zero.  (Actually an important figure to see at this point would be gallons per hour consumed in idling, which, in most heavy duty trucks is between 0.5 and 1 gallon per hour – wasted fuel – and that gallons per hour figure may change when things like air conditioning are switched on or off).

On the same gauge you can also see some wildly efficient numbers.  For example, when you coast, you can potentially see fuel mileage number in cars that exceed 99 mpg!! Of course, it is important to realize that the you will only be getting that number when you are off the throttle and rolling at a reasonable speed – you can hardly say that you are able to get “over 100 mpg in my car” because it really isn’t an accurate view of what the vehicle will get over the course of a tank of fuel.

Instantaneous fuel economy values are great for helping to see whether or not your Ecodriving is making a difference.  For example, you will be able to get immediate feedback under various acceleration loads on your fuel economy.  If you are aggressive with the throttle, your instantaneous readout will be very low, and the more moderate your are with your throttle usage, the higher your instantaneous number will be.

Its like having a coach in the car with you, helping you on a real-time basis to get better fuel economy and to perfect your Ecodriving technique. You do have to take the time and the effort to watch the numbers of course, but the information can really help you to achieve that increased level of fuel efficiency.

Next up is average fuel economy.

The average is a much better evaluation of what fuel mileage you are getting with the vehicle based on your driving habits and the type of driving that you need to do.  Average fuel economy fluctuates less and is the mpg figure that you are achieving since you last zeroed out the gauge.

Some people like to zero out the gauge between fill-ups and then challenge themselves to get a better number by the time they need to fill up again.  I personally do that all the time!

Astute drivers will notice that the average mpg figure will jump up and down more frequently immediately after the gauge has been zeroed out, and will stabilize more and more as time since that zero-out goes by.

Of course there are many other metrics that can be used to determine fuel use efficiency, but from a driver standpoint for in-cabin information, instantaneous and average fuel economy is a must.

Ecodriving – it works.


About Mike Speck

Lead facilitator and Master Ecodriving trainer for Ecodriving Solutions.
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