It's been a rough time for the official fuel economy figures for the Ford C-Max Hybrid. When the car was released in 2012, Ford made a huge deal about how it would beat the Toyota Prius V, which was rated at 42 combined miles per gallon, 44 city and 40 highway. The Ford? 47 mpg across the board.

How did Ford come to this place, where its Prius-beater turned into an also-ran?

Well, after hearing customer complaints and issuing a software update in mid-2013, then discovering a real problem with the numbers last fall and then making a big announcement last week that the fuel economy ratings of six different 2013 and 2014 model year vehicles would need to be lowered, the C-Max Hybrid has ended up at 40 combined, 42 city and 37 highway. In other words, the Prius trumps it, as daily drivers of those two vehicles have known for a long time. The changes will not only affect the window sticker, but also the effect that the C-Max Hybrid (and the five other Ford vehicles that had their fuel economy figures lowered last week) have on Ford's compliance with greenhouse gas and CAFE rules for model year 2013 and 2014.

How did Ford come to this place, where its Prius-beater turned into an also-ran? There are two technical answers to that question, which we've got below, as well as some context for how Ford's mistakes will play out in the bigger world of green vehicles.

2013 Ford C-Max Hybrid

Let's start with Ford's second error, which is easy to do since we documented it in detail last year (the first, needing to do a software update, was also covered). The basic gist is that Ford used the general label rule (completely legally) to test the Fusion Hybrid and use those numbers to figure out how efficient the C-Max Hybrid is. That turned out to be a mistake, since the two vehicles are different enough that their numbers were not comparable, despite having the same engine, transmission and test weight, as the rules require. You can read more details here.

Ford's Said Deep admitted that the TRLHP issue is completely separate from the general label error from last year.

Now let's move on to last week's announcement. What's interesting is that the new recalculation of the MPG numbers – downward, of course – was caused by a completely separate issue, something called the Total Road Load Horsepower (TRLHP). Ford's Said Deep admitted to AutoblogGreen that the TRLHP issue had nothing to do with the general label error from last year. "When we retested [the C-MAX Hybrid] last summer, we had not yet run the production vehicle validation tests that revealed the error related to how we correlate wind tunnel results into the TRLHP model," he said.

So, what is that model? Well, it's not easy to understand, but two detailed places to dig in are here and here (PDF). Ford's announcement yesterday said that:

TRLHP is 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.

The EPA described TRLHP to AutoblogGreen this way:

When using the dynamometer testing, certain factors/inputs need to be accounted for so that the test is as accurate as possible in reflecting real-world conditions. One of these factors is TRLHP. The TRLHP is derived from an engineering model and is validated from vehicle track testing. To calculate it, one must account for different variables such as crosswinds, aerodynamics, and tire friction.

In Ford's case, it wasn't just the TRLHP number that was off. Raj Nair, Ford's fall guy for hybrid mpg overstatement, told reporters that, "we do a physical wind tunnel test, and then use a correlation factor to enter that into the engineering model – which is then the total load horsepower test. The error was in the correlation factor in the model."

2014 ford fiesta

It's not only the C-Max Hybrid that was downgraded yesterday. The C-Max Energi, Fusion Hybrid and Energi, the Lincoln MKZ and most versions of the 2014 Fiesta were also acknowledged to be less efficient than previously stated. Despite all of these revisions – plus the Hyundai/Kia mpg errors – the EPA told AutoblogGreen that it doesn't expect that we'll see more changes in the future:
We generate over 1200 labels each and every year, and these three re-labelings represent a tiny fraction of that amount. With the majority of consumers achieving or bettering the label fuel economy estimates, based on consumer data provided to fueleconomy.gov and other websites, we are confident with vehicle test results and fuel economy label values.
Despite the wording of the EPA's press release that made it sound like the government agency pressured the automaker to change the MPG rating, the EPA confirmed that Ford came to the government with the news:

On March 28, Ford alerted EPA that they had identified a possible error affecting their fuel economy values. EPA immediately began working with Ford on an extensive re-testing program to correct the error, overseeing Ford's fuel economy tests, and also conducted independent testing at our Ann Arbor lab to confirm Ford's results. Under EPA regulations, Ford is required to correct fuel economy labels on affected vehicles within fifteen days.

Electric vehicle supporter and star of Who Killed The Electric Car? Chelsea Sexton said that Ford deserves credit for the, "the straightforward announcement, apology, and goodwill payments" and that the real interesting issue will be, "how the increased focus on these numbers affect EV range claims used by automakers in marketing, if not on Monroney stickers. Given the consequence to new drivers and, ultimately, the success of EVs, overly optimistic range numbers are the perfect example of 'just because you can, doesn't mean you should'."


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    • 1 Second Ago
  • 87 Comments
      GCG
      • 7 Months Ago
      Well, after last software update to allow up to 70mph in electric mode, getting 45MPG mixed in our 2013 C-Max hybrid. No complaints.
        Ross
        • 7 Months Ago
        @GCG
        Those stats tell alot about your driving style and not much else...Im convinced you'd be getting 60mpgs in a Prius ;-)
          GCG
          • 7 Months Ago
          @Ross
          Except I would have to 'drive' a Prius. That's a penalty box on wheels. Driving style hasn't changed since getting the car, software update made a big difference. Since interstates are 60mph here, and everyone drives 65+, electric mode cutting off at 62mph verses 70+ makes world of difference.
      Grendal
      • 7 Months Ago
      Ford is a really big company. All this is BS to backtrack on what they did. They played the game of knowing there was a problem but ran with it so they could advertise the higher MPG. To an extent all large and small companies do it with advertising. However, Ford calculated out that having the high initial number would stick in their customer's head. I'd bet that even now there are people that will tell you the C-Max gets 47 MPG. If they had just fudged the number then there wouldn't have been such a big backlash. They wanted to beat Toyota and paid the penalty.
      • 7 Months Ago
      My last tank got 138 mpg. I'm happy. Very reliable car
      johnnythemoney
      • 7 Months Ago
      It seems to me that TRLHP is a contorted way of naming the required power to have the car travel at constant speed, said power increasing at higher speeds. In other words, they screwed up their testing.
        Rotation
        • 7 Months Ago
        @johnnythemoney
        Correct on all fronts. You calculate the power required to travel at speeds, then you punch those load figures into the dynamometer when running the tests. If you get a low TRLHP, then the engine works less hard during the test and you get better mpg. And Ford knows it. They did it on purpose. Why it is done covered pretty well at this link: http://tinyurl.com/kpu5hvz And it indicates that recently (as mpg as been more important), the gap between the proper value that should be used and the ones the car companies determine has been increasing. In other words, the companies have been cheating more and more.
      • 7 Months Ago
      I'm in the unique position to compare the MPG of the plug-in Prius to the plug-in C-Max. I have owned them both and am now driving (and loving) the C-Max. I use it as a daily driver with each way being around 10 miles. I am getting MUCH better MPG with the C-Max because of issues that are not discussed very often. 1) Prius always starts engine when cabin needs heat. It could not be preheated while plugged in. The C-max can be preheated or pre-cooled while plugged in and therefore will not start the engine unnecessarily. 2) I can get about 20-23 miles on EV with the C-Max so I can do many more around town trips without ever starting the ICE. After 1300 miles, the C-max has over 3/4 tank of gas left in it. If you put a lot of miles on your car, the Prius will be better. On the other hand, the C-Max is a far superior car in every way. ie: comfort, handling, cornering, passenger room, upscale interior etc. The Prius does have more room for stuff when you fold down the rear seats but my costco runs have not been hindered by the C-Max's room. I would not go back. The Prius is basic transportation with good MPG. I'd much rather be driving the C-MAX (and in my case getting much better gas mileage).
      Mike
      • 7 Months Ago
      Anyone who believes advertised economy figures is crazy. I thought it was general knowledge that advertised MPG numbers are usually about 20% higher than in real life? The fact that manufacturers can advertise such blatantly unrealistic numbers is a different issue.
        Anderlan
        • 7 Months Ago
        @Mike
        Sure, trust but verify. But you're flat out wrong about your general knowledge. The EPA numbers are usually off by less than 10%, and sometimes they're wrong in your favor. Ford managed to hit 20%. They lied. In bad faith. EOF.
        Neez
        • 7 Months Ago
        @Mike
        My Subaru is spot on at 27mpg highway. My Prius is getting about 2-4mpg more than advertised. Yet, i had a CMax Hybrid as a rental, granted it was at about 1000feet more elevation than i normally drive, i was getting about 37-38 hand calculated mpg and drive mostly highway. Yet in my 2011 prius with 3 guys in it, driving 70-80mph all highway,i got 48mpg hand calculated. Normally by myself, i get 50-52mpg average hand calculated over a full tank The EPA changed the rating standards in 2008, it was suppsoed to be more representative, and i think they did a decent job. But obviously there is room for cheating.
      GoSpeedRacerGo
      • 7 Months Ago
      That may be true, but why wouldn't Ford want to make sure their numbers were relatively accurate, especially for high profile vehicles like hybrids? This just makes them look bad and momentarily takes the spotlight off of GM.
      Dimas
      • 7 Months Ago
      All garbage. They lied. Let's take a step back from all the technobabbly excuses like "TRLHP", "correlation factor" and "dynamometer testing". How is it possible that a bunch of high-paid, well-educated managers and engineers signed off on these bogus figures without realizing that—wait a minute—forget the ridiculously complex computer models and calculations and simulations, in real life the car actually can't come anywhere close to the 47 MPG figure? Any person driving that car with a full tank of gas would realize something was really wrong with the numbers they got. Why did the mad scientists in France and Switzerland built a monstrous 27 km-long machine underground called the Large Hadron Collider? It's because to figure out whether something is real, you have to test it for real, fools.
      Matt
      • 7 Months Ago
      While I'm not usually one to advocate increased government regulation, it's clear that the auto industry is incapable of performing their own fuel efficiency testing/labeling. Have the EPA run every new car around a test track for a full tank of fuel according to a prescribed speed schedule that corresponds to the average American's commute. Record that number and stick it on the window sticker. Can't be any worse than the mess we have now.
        x19x19
        • 7 Months Ago
        @Matt
        Even better - take 10 cars, off the line and give they to drivers in different parts of the country. Have them each dive 1000 miles and then download the data. The number will be the actual mileage you will get owning the car in real world, mixed driving, conditions.
        Spec
        • 7 Months Ago
        @Matt
        We gave them a chance to 'self-regulate' . . . and they abused it. They should lose their privileges. At the minimum, all Hyundai and Ford cars should be EPA tested.
        Ryan
        • 7 Months Ago
        @Matt
        The EPA thinks people should be driving 55mph, like they should. The numbers work at those speeds.
        cdrami
        • 7 Months Ago
        @Matt
        That wont work because of variable conditions especially the weather. Temp, Humidity, windspeed, wind direction, and tire all play major factors. Its even more amplified now because of turbos.
          Matt
          • 7 Months Ago
          @cdrami
          In my field (aerodynamics) we correct everything to coefficients that are independent of environmental variables. The EPA could correct for air density and wind, tires are a non-issue (test with the OEM tires), and humidity doesn't have a first order effect. Their error couldn't be more than Ford's >15% error.
        mapoftazifosho
        • 7 Months Ago
        @Matt
        fuelly.com helped to create awareness for this...
      Tiberius1701
      • 7 Months Ago
      And filling the tank!! LOL
      Will
      • 7 Months Ago
      Why is it that these automakers always make "mistakes" than make the MPG higher? I don't remember anyone ever revising their fuel efficiency because they accidentally made it too low.
      Joe
      • 7 Months Ago
      While some people think there is a conspiracy at work here, I am here to tell you that you have no proof and should be ashamed of accusing perfect strangers of being deceitful liars. You have bigger issues than Ford or Hyundai/Kia. Mistakes in complicated calculations are all too common. Also, when you are seeking a certain result, one that is expected perhaps, when the result is achieved it is essentially self validating. Only when the expectation is not met, do we double and triple check the figures. That is because the engineers and mathematicians are optimists and the accusers of wrongdoing are pessimists.
        Neez
        • 7 Months Ago
        @Joe
        Wrong, engineers are typically realists, only optimists during the design phase. I myself am an engineer. I've work in product validation(field testing) and now work on the innovations side(conceptual). Trust me, ford knew very well that the figures were crap. You're going to tell me, they don't have a fleet of field test vehicles driving around the country at any given time?????? If they don't, that's the worst engineering i've ever heard of. They have a fleet of test vehicles, i'm sure the test drivers are documenting the real world fuel economy numbers, and i really don't see at least 1 engineer at some point saying that the numbers don't equate, that their lab model does not correlate to the real world. I have a friend that works in our simulations department, he works closely with the lab and field test to make sure his correlation factors are aligned with the real world, so his models are more accurate. He's constantly cross checking and validating to make sure. There's no way a company as big as Ford has crappy engineers that don't make sure their simulation and lab models are correct. They had to have fudged that factor on purpose, so that if ever questioned by the EPA, they could come back and show them the data, so it looks justifiable and make them less liable for inaccuracy.
        Spec
        • 7 Months Ago
        @Joe
        When millions of dollars are at stake and the "mistakes" all occur in favor of them . . . it is not a mistake.
        Dump
        • 7 Months Ago
        @Joe
        My office pool car is the C-Max Hybrid. Whenever I can get it, I drive it hard & fast usually driving 10-15 mph above posted speed limit. It has such strong acceleration - which surprises most everybody on the road with me. Instant passing power & does great on long hilly stretches of highway. With my driving habits, I can only get 36mpg on the hwy; but I'm realistic about it though. If I drove slower, I'm sure I could get 40-42 mpg hwy easily. Just seems like Marketing dept made some (minor) adjustments to the fuel ratings information & no one bothered to correct them on it b/c the hype-engine was in full swing. Dealers saw the advantage & jumped on it b/c it was info released directly from Ford sites. Dealers didn't effectively warn new car buyers that actual driving habits & conditions will effect actual fuel usage. Consumers assumed the the ratings were real & obtainable - discounting any of their own daily driving habits (aggressive driving, speeding regularly, hard stops, hard acceleration).
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