New study finds drivers should not rely on their vehicle’s “miles to empty” display


(WEHT)– In-dash fuel economy displays estimate the number of miles a vehicle gets per gallon. This includes showing how many “miles to empty” a car has. AAA tested the accuracy of these systems and found their estimates vary significantly over shorter trips. Speed and acceleration also affects the accuracy of the “miles to empty” function.

Drivers could be taking an unnecessary risk if they over on their car’s “miles to empty” display too much which pertains to most drivers. According to a AAA consumer survey, 74% of drivers use their “miles-to-empty” display when they are low on gas to decide when to fill up their tank with gas.

“While motorists have fuel economy on their minds, they shouldn’t push their vehicles too close to the ‘E’ mark,” said Mike Hoshaw, vice president of automotive services, AAA East Central. “While the systems tested were fairly accurate, changes in speed, acceleration and distance produced noticeable fluctuations in the systems’ accuracy.”

On average, the fuel economy display of the vehicles tested showed a relatively low error of 2.3% as compared to the fuel economy measured by the dynamometer. However, individual vehicle error varied greatly, ranging from −6.4% to 2.8%. The negative number indicates that one test vehicle overestimated fuel economy by 6.4% or 2.2 mpg, while another underestimated it by 2.8% or 0.9 mpg. These specific results suggest that each vehicle reacted to changes in driving differently, and that the accuracy can be impacted by driving style and conditions.

The information displayed by these systems can give drivers a clearer picture of how their specific driving habits influence their fuel economy. To do this, drivers should reset their vehicle’s trip data after filling up, and then watch how their fuel economy display changes as driving conditions change.

With gas prices reaching their highest point in seven years, AAA has some recommendations to maximize the money you spend on gas. This includes:

  • Planning ahead and running multiple errands in one trip, and whenever possible avoid times of day when traffic is heavier.
  • If you own more than one car, use the most fuel-efficient model whenever possible.
  • Avoid hard acceleration to maximize fuel economy, and always inflate your tires to the recommended pressure found inside the driver’s side door or owner’s manual.
  • Remove unnecessary and bulky items from your car
  • Minimize your use of roof racks and remove special carriers when not in use. (Smaller cars weighed down by heavy cargo will have a greater reduction in fuel economy than larger models designed to carry more weight.)
  • In hot weather, park in the shade or use a windshield sunscreen to lessen heat buildup inside the car. This reduces the need for air conditioning to cool down the car.

While these tips will help improve fuel economy, AAA reminds drivers it’s best to always have at least a quarter of a tank of gas. This will ensure drivers have enough fuel in case of unexpected delays but also helps to prevent fuel pump damage that can occur when a vehicle’s gas tank is regularly run down to empty.

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