Ford took advantage of EPA loophole big enough to drive a hybrid car through

Consumer Reports data show optimistic mpg estimates may not be limited to C-Max

Published: August 16, 2013 02:30 PM

America's fuel economy labeling requirements are full of loopholes, and Ford found a way to drive a hybrid car right through one.

After owners complained that they couldn't get close to the advertised 47 mpg from the C-Max Hybrid, and we reported an average of just 37 mpg in our instrumented fuel economy tests, it became clear that something was wrong with the C-Max's rating. Yesterday, Ford announced a new 43 mpg rating for the small wagon, noting that it had simply applied the fuel-economy rating of the larger, sleeker Fusion Hybrid to the C-Max, as allowed under current EPA rules. (Read: Ford lowers C-Max Hybrid fuel economy rating, makes more updates for 2014.)

EPA rules specify that if two cars use the same engine and transmission, and fall into the same weight class, automakers have the discretion to use the same test results for both, even if they only actually test one of them. The Fusion Hybrid and the C-Max use the same engine, transmission, and electric drive, and their weights fall within 35-pounds of each other. But unlike other cars that may share an EPA fuel-economy rating, the two cars are not remotely the same size or shape, nor do they even share platforms.

The new estimates are based on an actual test conducted by the EPA after the discrepancy with the ratings came to light. According to a written explanation by the EPA, when the car was first retested, it averaged just 41 mpg. Ford meanwhile, was scrambling to improve the C-Max's mileage and issued a suite of software updates that brought the rating up to 43 mpg in a second test.

All this got us wondering whether other cars may be benefitting from unrealistic ratings from the EPA, based on these "rules." So we searched our data for cars from the same manufacturers that share the same engine and transmission and have identical EPA city, highway, and overall fuel economy results, but got different mileage in our fuel economy tests. Other than the C-Max and Fusion Hybrid, we found six other pairs of cars that fit that description, from Ford, Chevrolet, Nissan, Toyota, and Volkswagen.

Make & Model CR overall mpg CR city/ hwy EPA overall EPA city/ hwy
Ford C-Max Hybrid SE 37 35 / 38 47 47 / 47
Ford Fusion SE Hybrid 39 35 / 41 47 47 / 47
Ford Fusion Titanium (2.0T) 22 14 / 33 26 22 / 33
Lincoln MKZ 2.0 EcoBoost 23 16 / 34 26 22 / 33
Chevrolet Equinox (V6) 18 12 / 25 19 16 / 23
Chevrolet Traverse 16 11 / 23 19 16 / 23
Nissan Frontier (V6) 15 11 / 21 16 14 / 19
Nissan Xterra 17 12 / 23 16 14 / 19
Lexus ES 350 25 17 / 35 24 21 / 31
Toyota Avalon Limited (V6) 24 16 / 34 24 21 / 31
Toyota Land Cruiser 14 10 / 20 15 13 / 18
Toyota Sequoia 15 10 / 21 15 13 / 18
Volkswagen Golf TDI 38 27 / 49 34 30 / 41
Volkswagen Jetta SportWagen TDI 36 25 / 49 34 30 / 41

We looked up their EPA test results and found that all 14 cars use a mathematical derivation formula in lieu of an actual test. EPA doesn't publish the formula used, so we can't tell if one model's estimates are adjusted in any way relative to one another.

This doesn't really prove anything underhanded, though. Looking through the published EPA data, more than 80 percent of all cars use a mathematical formula to derive their fuel economy estimates—something Consumer Reports never does (Learn how Consumer Reports tests cars.)

We did find that some types of cars are slightly more likely to be tested. Japanese automakers, for example, are more likely to test each of their hybrid models individually. And  German automakers use calculations 60 percent of the time.

Using calculations may be understandable given that EPA rated more than 1,160 model variations for 2013. That would be an awful lot of testing. But that doesn't help consumers know how to find cars with the best mileage. Since automakers conduct the vast majority of the tests, we think the EPA should hold their feet to the fire to test more models that might not match other similar models on which their estimates are based. And indeed, EPA has said it plans to revise the rules allowing vehicles to rely on another vehicle's test results and is adding 30 staff members to its fuel economy compliance division to improve enforcement.  Consumers have the reasonable expectation that the fuel economy on a window sticker is actually based on that model.

That said, the C-Max may be an outlier. Few in the auto industry expected it could approach 47 mpg in the real world, or that its mileage would be very similar to the Fusion hybrid's. Ford should have known this, too, and using the same rating resulted in Ford's shooting itself in the foot because of the way a PR campaign of triple 47 has now backfired. In reality, Ford's hybrid technology is impressive, but that narrative got lost because of the overpromising.

Consumers can take heart in one thing: The C-Max's new 43 mpg rating represents a real improvement in accuracy and mileage due to the EPA tests and Ford's enhancements.
When the EPA first conducted an actual test on the car without Ford's added software updates, it delivered just 41 mpg. And for 2014 models, Ford is using some tried-and-true strategies to boost the C-Max's mileage even further, raising the gear ratio and adding aerodynamic improvements that should boost highway mileage, the area where the C-Max fell furthest short.

We'll look forward to retesting the C-Max after we can buy one with all of these updates. And as before, we will post the results of our tests to empower consumers to make an informed purchase decision.

Visit our guide to fuel economy, with tips to save fuel now and lists of the most fuel-efficient cars.

Eric Evarts

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