PITTSBURGH — New research finds drivers should not rely too heavily on in-dash fuel economy displays.
In-dash fuel economy displays estimate the number of miles a vehicle gets per gallon, including how many “miles to empty” a motorist has. AAA tested the accuracy of these systems and found their estimates vary significantly over shorter trips and can depend heavily on speed and acceleration. This means drivers could be taking an unnecessary risk if they over-rely on these displays, which 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).
“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.”
In collaboration with the Automotive Research Center (ARC) of the Automobile Club of Southern California, AAA used a dynamometer (essentially a treadmill for vehicle testing) to run selected vehicles through a series of simulated driving scenarios to determine the accuracy of the fuel economy estimation and range value (aka “miles-to-empty”) systems.
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.
