Don't rely too much on that 'miles-to-empty' warning for gas, AAA says

TEXAS (KTRK) -- We've all been there.

You're driving to work and suddenly, you realize you have 15 miles left until you run out of gas, according to your car.

But how accurate is that "miles-to-empty" warning? Well, research shows you shouldn't rely on it too much.

According to AAA Texas, researchers tested the accuracy of these systems and found the estimates vary over shorter trips or are dependent on the consistency of things that affect gas mileage, like speed and acceleration.

This means drivers could be taking an unnecessary risk if they over rely on these displays.

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According to a recent AAA survey, 74% of drivers say they use their "miles-to-empty" display to decide when to fill up.

"People want to get the most out of a tank of gas, especially when prices are higher," said Megan McKernan, the manager of AAA's Automotive Research Center. "Collectively, the systems we tested were relatively accurate, but a closer examination of different driving scenarios revealed significant variability based on changes in speed, acceleration and distance."

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On average, the display system of the vehicles tested showed a relatively low error of 2.3% compared to the gas measured by the dynamometer.

However, individual vehicle error varied greatly, ranging from -6.4% to 2.8%.

That means one test vehicle overestimated fuel economy by 6.4% while another underestimated it by 2.8%.

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These results suggest that each vehicle reacted to changes in driving differently, and that the accuracy can be impacted by driving style and conditions.

"We ran our test vehicles through different driving situations ranging from cruising at highway speeds to being stuck in traffic to typical city driving," said McKernan. "Despite the irregularities our testing found, a vehicle's fuel economy display is an important tool to understand how different driving styles impact how efficiently a vehicle uses fuel."

AAA says drivers should reset their vehicle's trip data after filling up, and then watch how their fuel economy display changes as driving conditions change.

To avoid running out of gas, AAA Texas recommends drivers watch their gas gauge and fill up when it reaches a quarter of a tank.