Mitsubishi plans to begin publishing “real world” mileage numbers on its vehicles, starting with the Outlander PHEV. The plug-in hybrid is rated at 148 mpg in Europe, but generally achieves about 90 mpg in the real world. The difference is in how testing versus reality compare. They aren’t usually the same, especially with hybrids.

The U.S. Environmental Protection Agency has modified its testing over the years to become closer to the real-world economy most of us will see. Having test-driven dozens of cars with this in mind, I’ve noted that most are generally within an acceptable margin of error (usually 5%, certainly under 10%). Yet when Ford introduced the C-MAX and used MPG numbers based on the larger, but far more aerodynamically efficient Fusion, the disparity created a huge PR mess for the company and sales were definitely affected.

In order to avoid that, at least in Europe (no word on whether this would come to the U.S.), Mitsubishi has promised to promote real-world numbers for their cars in terms of MPG. The company has the ambitious plan to offer a plug-in hybrid version of all of its cars within the next five years, so having actual mileage on display would be a good thing. With the Outlander PHEV, 90 mpg sounds stellar for a small crossover, but becomes pathetic when the expectation is 148.

How will the numbers work? Mitsubishi hasn’t released details, but it would be based on test drives and early ownership mileage for buyers and dealerships, using the car’s computer to track and calculate.

“We’d like to do a graph, maybe just a figure, starting with the PHEV but then rolling it out to other cars. It would come from customer information,” said Lance Bradley, MD of Mitsubishi UK to AutoExperess. This suggests buyers could input their real world fuel economy to make it clear to prospective owners what they should expect.

This is a good sign of openness and consumer-oriented marketing. We hope that other automakers take note and follow suit.