(AAA/WWJ) -- We've all done it — checked our car's 'miles-to-empty' gas gauge and mentally calculated how far we can push it before we have to fill up.
But new research finds drivers should not rely too heavily on those in-dash fuel economy displays.
AAA tested the accuracy of these systems and found their estimates vary significantly over shorter trips. The study also found that the systems 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 put to much emphasis on these displays.
That fact is especially true for the 74% of drivers who use their "miles-to-empty" display when they are low on gas to decide when to fill up, according to a AAA consumer survey.
To avoid running out of gas, AAA recommends drivers watch their gas gauge and fill up when it reaches a quarter of a tank.
Drivers should also reset their vehicle's trip data after filling up, and watch how their fuel economy display changes as driving conditions change.
"People want to get the most out of a tank of gas, especially when prices are higher," said Megan McKernan, manager of the 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."
In recent weeks, gas prices have skyrocketed to their highest point in seven years.
To offset some of this additional cost, AAA recommends drivers do the following:
-Plan ahead and run 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.
-Consider minimizing your use of air conditioning. Even at highway speeds, open windows have less effect on fuel economy than the engine power required to operate the air conditioning compressor.
-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 (and thus fuel) to cool down the car.
