When Ford announced that it was lowering the fuel economy ratings of its hybrids, plug-in hybrids, and 2014 Fiestas a few weeks ago, several of you emailed us asking why The Blue Oval was taking the measures. According to a news release issued by the automaker, the reason that Ford lowered its MPGs pertains to an error with the dynamometer settings that determine fuel economy ratings.
While fuel economy testing involves many factors, Ford’s error was specific to a factor called “Total Road Load Horsepower”, or TRLHP. A vehicle-specific resistance level used in vehicle dynamometer testing that determines fuel economy ratings, TRLHP is established through engineering models that are validated through vehicle testing, including physical track tests referred to as coastdown testing.
Most, if not all, of the automotive industry uses these engineering models, which are consistent with EPA regulations. A major benefit to using the models is that they are more reliable and consistent than physical vehicle tests, which can exhibit great variability.
With all that in mind, here’s the explanation directly from Ford:
As an ongoing practice, Ford conducts tests on production vehicles to validate its engineering models. Based on coastdown testing of the Fusion Hybrid, the company found the TRLHP did not match the values used for the dynamometer testing.
Upon further testing, Ford also discovered an error specific to how we correlate wind tunnel results into the TRLHP model. Ford’s error was the result of a recent process change, which the company has since corrected.
Ford states that it has validated the TRLHP for the affected vehicles by conducting physical vehicle testing, while also putting in place enhanced validation tests for future vehicles to prevent the error from happening in the future.
The Motrolix Take
Better to be honest and open about these kinds of things. In that regard, we’re glad that Ford is addressing the fuel economy ratings for the affected vehicles and making good with existing customers in the form of payments, while making changes to its internal testing processes.
But once the dust has settled, we do wonder what kind of an effect the drops in MPG will have on Ford’s reputation (read: bragging rights), since its hybrids will no longer be able to list the impressively-high fuel economy numbers as before the drop.