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The Calibration Bench | Blog

Miles to Empty

Posted by The Metrologist on Sep 8, 2017 4:02:00 PM




How Accurate is the Mileage Prediction in Your Car

The last two vehicles I’ve owned have had a “miles to E” readout on the dashboard. As a measurement scientist and someone with a touch of OCD, I’ve always felt that the numbers never seemed to quite add up. I recently took a family trip and decided to record some numbers to chart and see how accurate the “miles to E” prediction really was.

The Experiment

When I filled up with gas in central Pennsylvania my miles to “E” indicator read 426 miles. I decided I would drive the 26 miles and reset my trip odometer to 0 when the miles to “E” indicator read 400. Initially, I was just going to track things in my head to see how it came out, but I figured someone else out there is as compulsive as I am and might be curious.

So, I recorded data points about every 25 miles or so to include: miles elapsed, miles to “E,” and average miles per gallon. I recorded the average miles per gallon because I was driving through the mountains so there was the possibility of mileage varying, but the data remained pretty steady after the first 50 or so miles.

This experiment was performed with my 2015 Ford Escape that has about 40,000 miles on it. The temperature varied from about 60 to 70°F for the 300 miles I tracked. With about 100 miles to “E” I was coming up on the border of New York so I cut the experiment off to fill up.

The Results

miles to empty mileage prediction alliance calibration


It was the large “adjustment” to the prediction that occurred about 100 miles into the journey that was most surprising to me. What is even more striking is the average miles per gallon started at 28 and leveled off at about 30 mpg at 100 miles in, so you would think any adjustment would have went in the other direction.

What I actually found in this case was that the prediction for 300 miles actually only actually took me 271 miles. That is, in all honesty, a lot better than I thought it would be.

I also compared the dash display of the average mileage to my next fill-up and was impressed to see that when I averaged the data I collected (excluding the points less than 50 miles) the dashboard readings of 29.93 mpg matched the gas pump calculation of 29.83 mpg.


In the case of my vehicle under those conditions, the prediction was within 10% of actuality. I consider that pretty good given the fact that it is a guess, at best, and depends on a large number of external factors that can’t be controlled or known about beforehand. I plan on repeating this experiment a few times to see what other results I come up with.