‘Miles to empty’ displays may not be as accurate as you think

AAA recommends getting gas when your fuel gauge dips to a quarter of a tank

SAN ANTONIO – If you rely on your car’s “miles-to-empty” display to determine when to coast into the gas station for fuel, that may be a risky move, according to new research from AAA.

Robert Garcia says he watches the range gauge on his wife’s car count down, way down before he tops off the tank.

“So, I wait to four, three, then we go to the gas station,” he said.

He’s hardly alone. Seventy-four percent of drivers rely on that display, according to AAA. But should you trust it as you coast on fumes?

“They are not always entirely accurate,” said Josh Zuber with AAA.

In partnership with the Automotive Research Center at the Automobile Club of Southern California, AAA tested the accuracy of dash displays that estimate fuel economy and range.

Collectively, fuel economy was reasonably accurate, although there were some significant variations from test to test. One vehicle’s fuel economy was overstate by 6.4%, or 2.2 miles to the gallon, according to the study.

But can you trust the “miles-to-empty?”

The testing found discrepancies and variations, particularly on short drives. They found the estimate is based on recent driving patterns to determine future mileage, and that may not be totally accurate. For example, if you were to switch from highway driving to city start-and-stop traffic, your car could overestimate the range until it detects the new driving patterns.

“AAA found that the accuracy of these systems relied a lot on drivers’ driving habits,” Zuber said.

Instead of flirting with a truly empty tank, AAA recommends gassing up when the needle hits a quarter of a tank.

Running out of gas isn’t the only reason not to run the tank near empty.

“Drivers who consistently run their vehicle to empty before re-fueling could be doing costly damage to the fuel pump,” Zuber said.

Although gas prices have dipped slightly in recent days, they are still near seven-year highs.

To make the most of a gallon, AAA suggests you make sure your tires are properly inflated, avoid jack-rabbit starts, avoid speeding, plan ahead to combine trips, minimize the car’s AC, and remove unnecessary cargo.

About the Authors:

As a consumer reporter, Marilyn is all about helping people stay safe and save a buck. Since coming to KSAT in 1985, she’s covered everything from crime to politics, winning awards for her coverage of the Mexican Mafia, Oklahoma tornadoes, children’s transplants, an investigation into voting irregularities and even a hit-and-run Santa Claus.

Joshua Saunders is an Emmy award-winning photographer/editor who has worked in the San Antonio market for the past 20 years. Joshua works in the Defenders unit, covering crime and corruption throughout the city.