We took six of the top-selling, most fuel-efficient cars in the U.S. and pitted them against each other. How’d they do in our mileage drive?
While Nissan's redesigned 2013 Altima may have the highest EPA-estimated mileage rating among family sedans, its trip computer had the largest discrepancy with our calculations at the pump. After a 185-mile loop, the Altima's trip computer read 4.38 mpg above our calculations — far higher than the variances we observed for the 2013 Ford Fusion, 2013 Honda Accord, 2013 Hyundai Sonata, 2013 Kia Optima and 2012 Toyota Camry. The Altima won the day's trip-computer mileage with an observed 35.9 mpg, but its calculated pump mileage — 31.52 mpg — landed it a third-place finish behind the Camry and Accord.
We took six contenders on a daylong mileage loop in mixed city/highway conditions. Per our usual mileage-challenge procedures, we began and ended at the same gas pump, swapped drivers over roughly equal chunks of seat time, kept windows and sunroofs closed and avoided cruise control. With cool temperatures and low humidity, we kept air conditioning off this time.
At day's end, our calculated pump mileage amounted to less than 1 mpg difference from what the trip computers read for five of the six cars, but the Altima's was off by 4.38 mpg. Why the discrepancy?
"Fuel economy meters are provided for the convenience of our customers, but are subject to a number of variables that necessarily limit their precision," Nissan told us in a statement. "After being told of the reported variance between observed fuel economy and the meter during the Cars.com test, we brought the subject vehicle to our technical center and ran fuel economy testing with it and several competitor vehicles. While we were not present for the Cars.com test, and therefore cannot comment on it, our own testing did not duplicate the large variance reported by Cars.com, and instead demonstrated that the meter was working as designed and within our internal engineering specifications. The vehicle meter performance was also found to be within the same range of tolerance as competitor vehicles tested in the same manner."
None of our six cars were way off-label; it’s crucial to note that all of them came very close to their EPA combined mileage ratings.
We've explored some of the inherent inaccuracies in fuel-pump calculations before, as well as the potential for trip computers to skew one way or another, which data from at least one government study suggest. For this mileage drive, we averaged our two figures for the final mileage: our observed mileage and the mpg readouts. The Altima won the day while the Accord came in second. Although the Camry, Sonata, Optima and Fusion have the same combined city/highway EPA rating of 28 mpg, the Camry performed 2.7 mpg (9.5%) better than the last-place Fusion. The Optima and Sonata, which are platform siblings, fell between those two with nearly identical mileage.
Although the Altima's trip computer varied the most from our pump calculations, the Accord's was spot-on. We calculated 31.85 mpg, while the car's computer rang up 31.9 mpg.
Here are the results: