Fuel economy estimates to become more accurate

In a move that promises to provide consumers better fuel economy insights, the EPA has announced a new fuel economy test guidelines for automakers. The new guidelines detail how fuel economy will be measured over a wider variety of speeds than previously specified.

The changes are designed to bring EPA fuel economy labels more consistently in line with cars' real-world performance, especially with hybrids.

Most conventional cars fall within one or two mpg of their combined EPA estimates when Consumer Reports runs them through our own battery of fuel economy tests. But most hybrids and other high-mpg cars fall far short.

Several automakers in recent years have had to restate fuel economy labels after the EPA found discrepancies in routine audits. For example, Ford lowered the fuel economy labels for the C-Max Hybrid and Fusion Hybrid from 47 mpg combined to 40 and 42 mpg combined, respectively, in 2012. Hyundai paid a record fine of $360 million in 2011 for overstating the fuel economy of a dozen models. Mercedes-Benz and Mini have also revised labels on some models.

A Consumer Reports analysis showed that EPA labels for 90 percent of car models fell within 1 or 2 mpg of the results of Consumer Reports test findings. But the last 10 percent consisted largely of hybrids and other high-mpg vehicles.

For more, visit our Guide to fuel economy.

It has never been clear whether automakers were intentionally cheating fuel economy tests, or if they simply had trouble following a set of arcane guidelines, especially when it comes to the most technologically advanced modern cars.

"This guidance is another step in enhancing our oversight of our fuel economy labels to ensure that consumers have reliable fuel economy information, and that EPA's historic greenhouse gas emissions standards for cars and light trucks achieve the environmental results promised to the American public," the EPA said in an emailed statement.

Since the new guidelines don't actually specify any new test cycles, these updates to the test guidelines are seen as a way to allow the EPA to update its test requirements quickly as technology progresses without having to return to Congress to update test requirements.

"It's good that the EPA is taking this issue seriously," says Jake Fisher, director of auto testing at Consumer Reports, "because consumers need to be able to rely on these window labels."

The new guidelines go into effect for 2017 models. We hope they provide more consistently accurate fuel economy labels for consumers – especially those interested in the most fuel efficient cars.

—Eric Evarts