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Ford’s math on hybrid fuel economy; standing by the C-MAX EPA ratings, acknowledging large real-world variance
15 December 2012
|Raj Nair outlining factors affecting real-world fuel economy in hybrids. Click to enlarge.|
At Friday’s event unveiling the new Transit commercial vehicle family for North America (earlier post), Ford’s Raj Nair, group vice president global product development, spent some time addressing the issue of the large discrepancy between real-world fuel economy results for the C-MAX hybrid and its EPA fuel economy ratings—47 mpg (5.0 l/100km) city, highway and combined—earlier highlighted in detail by Consumer Reports. (Earlier post.)
Basically, Ford is standing by the ratings as determined by the current testing protocols, Nair said, but added that “we absolutely agree with EPA that hybrids are far more variable in the test cycle compared to real world driving conditions in conventional vehicles. We are working closely with the agency to determine if any changes are needed for the industry relative to hybrid vehicle testing.”
|Nair highlighted as an example the delta between EPA ratings and Consumer Reports results for multiple hybrids in one of the CR tests. Click to enlarge.|
Nair noted that the Consumer Reports testing also found discrepancies in between real-world testing and EPA rating for hybrids from other manufacturers, and singled out a 19 mpg variance on a Prius as one example. One of the issues with the Ford results, Nair suggested, is that the performance of the vehicles as designed lends themselves to more sprited driving. Combining a “lead foot” with environmental factors can lead to the wide swings in fuel economy results, he said.
There have been some questions raised about fuel economy, so it is important to note that we have designed our hybrids to drive exactly the same as all our other vehicles, with the global Ford DNA. A key part of that DNA is “fun-to-drive”. We could have detuned the vehicles to maximize fuel economy like some of our competitors have done, but it would have been at the expense of a fun driving experience. And this would have meant that you would not be to take advantage of the 54 more horsepower that the C-MAX provides over the Prius.
Ford next-generation hybrids offer increased performance and extended electric modes up from from 47 to 62 mph. Tremendous advantage in fuel economy, but it also makes them more sensitive to spirited driving as well as to environmental conditions. Quite a few factors can affect hybrid fuel economy, more so than regular gas engines.
Among the differences Nair spotlighted were:
Speed: the difference between 75 mph and 65 mph can produce a 7 mpg difference in fuel economy.
Outside temperature: a temperature difference 40 °F and 70 °F can result in a 5 mpg difference.
Vehicle break-in: the difference from 0 miles to 6,000 miles can be a 5 mpg difference.
When I drive our hybrids home from Dearborn to Ann Arbor, when I am using all of our coaching tools, I consistently hit the combined number. Unfortunately, that’s not the way I usually drive. So when I drive that hybrid the way I drive my Shelby GT500, I typically lose about 12 mpg. That can be the difference between maximizing the tools available, versus having a little bit of a lead foot like I do.—Raj Nair
In its testing, Consumer Reports found the C-Max Hybrid delivered 37 mpg (6.4 l/100 km) overall, with 35 (6.7 l/100 km) and 38 (6.2 l/100 km) for city and highway.
Nair pointed out that some consumers are achieving results better than the 47 mpg EPA rating.
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