Consumer Reports "The mpg gap"

Link to the referenced story: Fuel Economy - Consumer Reports

 

Yeah, Consumer Reports is sort of nuts on city MPG tests. They still report 44 overall with 3G Prius. My lifetime is almost 51 MPG and that's with no special effort.

 

...the article does not seem to mention if CR is using E10, but I must presume E0 is being used if they do not cite this as a difference to EPA. So take 44 and subtract 3% for E10 on Prius sounds like they are too low.

 

Here's the post on the CR blog, where comments can be made.

 

I offer this in counter point to CR's stance.
Mileage Moment of Truth - We Put 40 Mpg Claims to the Test - Popular Mechanics

Drive sensibly and you should get close to EPA.

It might be prudent for some technologies, such hybrids and turbos, to be required to perform all 5 tests instead of just the two and use some type of fudge factor.

 

A posting of their procedure did mention using a local station. So it is likely E10 to begin with. Of course that means some cars are tested summer blend and others on winter. So between model comparisons with CR numbers start becoming guess work.

Oh, I now drive a car with a small displacement turbo and exceed the EPA highway by 11% on a 1/2 city, 2/3 highway commute. I do admit to not being the average driver.

 

I think when they say the largest discrepancy is in the higher mpg cars like hybrids, it is true depending on how you look at it and we see it all the time on PriusChat and the yahoo groups. If you look at it ratiometrically it is not true. If you look at it in absolute terms, then sure.

Give someone a car that gets 15mpg on the EPA test and they won't really care if it gets 14mpg. It is a 6.7% drop for that 1mpg. Nobody cares about 1mpg right? So in a Prius that is supposed to get 50mpg, nobody really cares if it gets 49mpg. However for the same "I don't care" percent, that is really 46.6mpg. We get posts here all the time of "why am I only getting 46mpg". So even though they are both 6.7%, the Prius shows it more.

We know from standardized testing that American math skills are way below normal. Show them 46.6mpg on a 50mpg car vs 14mpg on a 15mpg car and the 46.6mpg looks like it is very misleading and the car should be recalled and the maker tied to a stake and burned. 14mpg on a 15mpg car, who cares it is so close.

It is the same sort of bad math and science skills that allows Chrysler to sell Jeeps by touting they get the best range. It makes people think that 2 vehicles that get 400miles a tank are equivalent. One may take 20 gallons to go 400miles the other 10 gallons, but people don't see it that way or even question it.

Consumer reports is either lumped into the category of bath math, or it is playing/pandering to the crowd that has poor math skills. Neither are very flattering for what is supposed to be a reporting magazine. But I am guessing most of the editors and writers there are not the ones taking advanced math classes throughout school. When I was at university, the requirement for a bachelor of arts degree in one of the humanities said that you only need Algebra II as a minimum and most people did not voluntarily take more than that. I took Algebra II in 6th grade at the charter academy. We are sending people with 4 year degrees into the workforce that have the math skills of a 6th grader and then we wonder why they can't do math...

 

This is the sort of nonsense my work colleagues will produce to show how I'm being fooled into thinking the Prius is fuel efficient and that I should just drive a diesel.

My response is simple; They never hear me complain about the cost of petrol

I'm averaging 63mpg UK and I don't hang about and that includes heavy traffic at both ends of my commute. My best average on a slow drive to work without a/c was 89 mpg UK over 20 miles. I am yet to see any diesel do that, let alone one that can carry 4 passengers and their luggage with ease, do 0-60 in 10 seconds and overtake with ease.

(now if Toyota could make the Prius more reliable and rattle less I'd be happy)

 

how the heck does my leadfooted wife get 47mpg around town in her hycam?

 

Consumer Reports tests and rates all kinds of products, and typically their CR Best Buy's are lower priced or the best value against the competitors. So it's really puzzling how they don't get that driving for efficiency actually REQUIRES a certain driving style different from stomping on the gas pedal or brake pedal. But since driving style is not a product, they can't fathom how that would impact their results. I find fault with many auto test articles written by auto mag's too. When testers drive auto's, it's not their money on the line so they don't drive or act like it is - sort of like driving rental cars.

 

And they often quote the Prius as "noisy under acceleration". When? When you're hammering it at its limits, that's when. I drive quite hard with a lead foot and other than hard overtaking at motorway speeds or going up hill, the Prius is quiet.

 

In my research the Prius was one of the few fuel efficient models that seemed to deliver as advertised based on feedback on Fuelly and fueleconomy.gov. It is one of the reasons I bought it. If I'm buying a fuel efficient car, I want it to deliver the goods. I can get 30 mpg in a lot of cars.

Granted, the folks who bother to track at all may result in a skewed sample, but the same could be said for those in a Hyundai Elantra or Focus tracking at 29 mpg.

 

That would suck.

The last ~ 800 miles on my Prius vagon are at 58.7 mpg by the car meter. That is with AC most of time, about 50% highway/40% rural/10% city.

 

I have seen CR in the past frame this charge in terms of percentage off from EPA from their test drive. I don't know if the author this time was using the same metric.

I agree with Bob however that CR should publish the test protocol. If e.g. they have the test protocol set up for short distance braking that is fine so far as it goes, but then readers would be able to decide if they too drive like idiots and miss out on regen.

 

I see the problem of "real world driving" mpgs not matching up with the EPA tests as due primarily to the "organic software" operating the vehicle. Just look at the way people drive. Any "reasonable" driver should be able to meet the EPA combined mpgs. People drive entirely counterproductive to good gas mileage and then complain about the EPA numbers being too high.

This is kind of like taking a test at school, flunking it, and then complaining the test was too hard. When, actually a number of people in the same class got As or Bs. Well, guess what - they studied for it! People don't see a learning opportunity when there own mileage is significanltly below the EPA.

The media don't help the situation, sometimes they seem to just promote the issue - like the Car & Driver test of a Prius v that averaged 31 mpg over 480 miles! See Essentially a Small Minivan I own a Prius v and cannot conceive of how I could get that low of an average mpg short of seriously abusing the car.

I feel there are legitimate issues with the published EPA numbers in some cases - the Ford C-Max being one. We shall see how that plays out.

 

The disclosed/published Consumer Report (CR) vehicle fuel efficiency methodology does not disclose whether the engine is pre warmed up or not, whether 100% gas or 10% ethanol gas is used, and it also fails to disclose the time and distance covered on the test loops. The EPA test loop uses a pre-warmed up car, it uses 100% gas ( about 7 % more energy content IIRC), and the EPA test loops have a fixed published time-distance-acceleration-deceleration cycle as well. The published EPA testing methodology is more complete than the published-disclosed Consumer Report Methodology.

The Prius fuel efficiency is very sensitive to warm up cost and the time/distance it must travel. My guess is that lower Prius fuel efficiency results that the CR achieved in its test loop was because the CR likely tested with a cold engine, used E10 gas, and may have used shorter test loops.

With respect to what CR did disclosed, the CR city test loop requires that a driver must maintain specific speeds in certain sections - this would prevent Pulse and Glide or do Smart Braking and suggest CR drivers may do jack rabbit starts and run to a stop light which would hurt fuel efficiency. The CR city test loop also requires the driver stops the car at specific points for set idling times - so Driving without Brakes out and the only FE measure would be how well does the engine cut off tech works. The driving method used in the CR test loop is inefficient so it should not be a surprise that the CR fuel efficiency reports are much lower than what a skilled hypermiler can achieve on a Prius.

The CR Highway test loop is measured by driving at a steady 65 mph - which prevents the use of Driving with Load (gravity assisted acceleration) a fuel efficiency hi speed adaptable driving technique. All vehicles can achieve higher fuel efficiency if they drop their speed down to 60 mph or 55 mph - so again I am not surprise that the CR fuel efficiency reports are lower. However, in some places like like Texas where the post speed limit (PSL) can be as high as 80 mph - 65 mph is way too slow. At 80 mph in the rain - I was only able to squeeze 44 mpg on my Prius over 430 miles.

Disclosure: Over the last 3 years - I have been learning how to hypermiling a 2010 Toyota Prius III. I have public disclosed real world mileage logs under HyperDrive 1 - Cleanmpg.com and fuelly.com. I use 10% ethanol 87 octane regular gas exclusively. My daily commute is 15.8 miles with a drop/climb of 200 feet. and my mileage log represent the driving conditions of Washington DC metro area in all four seasons - winter, spring, summer, and fall - plus I do regularly do an annual Maryland to Michigan/Missouri 600-900 mile superhighway road trip - where I normally drive between 50 to 80 mph for over 8 hours. My computed at the filling station fuel efficiency has varied from 44 mpg to 71 mpg per tank and my overall average is 60 mpg.

 

For what its worth, the car mags all manage to get ridiculously low fuel economy, and tend to be all over the place. I'm guessing they must include their track time in the overall number they publish.

For example the 2013 Civic. C&D tested it on its own and they published 27 mpg. Actually not bad compared to the 28/39 rating. Motor Trend tested the car as part of its compact car comparison test and got 23.5. Fuelly folks are showing 34.7 for the '13 Civic. Motor Trend got 21.2 out of the Nissan Sentra. Fuelly is showing 30.3 right now. I can't imagine all Fuelly drivers are hypermiling. They probably just aren't beating on the car.

 

If, as I suspect and no-one knows, the CR test mandates where they must begin braking and where they must be stopped, they simply are braking so hard they get no regen. (we know the car mags do this) If you consistently brake without regen, your mileage will go down.

 

I see all the car mags numbers as what you will get while driving like an idiot, and Wayne Gerdes(clean.mpg) number for trying your hardest at hypermiling the car.

For car shoppers, the EPA numbers are still the best for comparisons between models. Knowing your percent of EPA in your current car makes them more useful. Fuelly can also be useful as long as the sample size isn't too small, and it covers at least a years worth of seasons.