Consumer Reports provides such feedback regarding disparity between their gas mileage test and EPA stickers only occasionally, such as with their evaluation of the C-Max. If they give a table for the cars they review somewhere in some issue as to "EPA sticker", "Consumer Reports road test", and "percent disparity", I would like to know where that table is. The impression I get is that 1) they regard their road test as a "ground truth" for fuel economy and think of the EPA numbers as "made up", 2) if a reader wanted the EPA number, they could go look it up on FuelEconomy.gov. Their road test has also changed over time, making it hard to compare a new car model against a 20-year old car, and yes, some of us keep cars that long. I can't find in Consumer Reports back issues a good description of their road test conditions.
Has Consumer Reports ever set up a road test to replicate the EPA test conditions and used that to quantify road test/EPA test disparity?
They only mentioned the disparity for the C-Max because it was large, even compared to the Prius, which also has such a disparity. The tone they took was that the larger disparity for the C-Max was evidence of Ford "gaming the system." They only mentioned in passing that the C-Max was also much less underpowered than the Prius, without any discussion as to whether this performance fully accounted for the difference in gas mileage, whether this was a tradeoff that a consumer would want to make, and whether driving the C-Max more conservatively made up for the shortfall in gas mileage.
Indeed, the large disparity in the C-Max could be evidence that Ford is gaming the system, but Consumer Reports didn't do anything to pursue this further, unlike the lab that found a disparity in the VW Diesels and dug deeper. It could be that Ford is legally gaming the system in optimizing the C-Max for the narrow range of driving conditions on the EPA test while giving it a transmission tuning making it "more fun to drive" in more "normal driving conditions", hoping that their consumers would be happier with the better acceleration and that consumers would be conditioned to believe that the "EPA numbers are made up, anyway, and no one ever gets those." Or it could be that Ford has "pulled a VW" and not get caught, but Consumer Reports has passed on investigating this deeper to find out.
Consumer Reports also appears to lack curiosity regarding outliers in their own test results. I remember a while back they tested a Dodge Neon back when Chrysler made a car with that nameplate, with a 3-speed automatic transmission to boot, that got in the mid 40 MPGs on a test where competing cars were in the mid to high 30's. Did they rerun the test as a "sanity check"? Do they even know what the variation is on their test between successive runs?
I also notice that their gas mileage rating can fluctuate, often downward, from year-to-year when they retest the same make and model of car. You also see this in the EPA numbers. Some of that may be transmission and engine retuning to trade more "pep" for less gas mileage, especially in the years when gas prices were in decline. But a consumer gets to wonder if the same kind of car can vary in gas mileage and by how much. That the expectation is that the EPA gas mileage is "made up" bakes into the system that it is hard to make the case that you bought a "lemon car" with bad gas mileage. A gas mileage complaint is really hard to make stick with the guys who sell and service your car because they will always turn it around and blame it on your driving. Did Consumer Reports ever try renting, say, about a half dozen cars of the same make, model, and year to see how consistent they are?
Yeah, yeah, Consumer Reports is a non-profit with limited resources in the amount of testing they can do. But given that gas mileage is such an important factor in satisfaction with an automobile purchase, and given that it is so hard to benchmark your car against a standard to check if you got a gas-mileage lemon (I suggest a method for a road test comparison against EPA -- can anyone tell me how to benchmark against the Consumer Reports road test as I don't even know what that road test is?), Consumer Reports could do more on this score. Remember, it wasn't Consumer Reports who uncovered the VW Diesel cheat.