Consumer Reports Prius Prime Review (Aug 3 2017)

As someone who lived in the San Francisco Bay Area for almost 40 years, albeit in the South Bay, San Jose area, not the City of San Francisco, I will have to admit that driving in dense urban city centers has not been part of my day-to-day experience. The City of San Francisco and the rest of the Bay Area are two different universes.

 

I don't think CR is better than EPA, because it appears uncontrolled, and if the results were submitted to a scientific or engineering journal, they would not be published without thoroughly revealing their methods.

I think you confused by the labels the EPA used. The city test cycle does mimic the center of a major city, but is actually closer what you'd see in a town. Here are the details on the EPA test cycles, Detailed Test Information. I suspect you don't hit that 56mph top speed, and I am confidant you don't take that long to get up to whatever speed you do achieve. It is a longer distance than your drive, which means you are paying more for the warm up penalty. Any trips under 10 miles are going to kill fuel economy in any car.

I had a 2005 Prius, and got 58 to 60 MPG in nice weather on my commute. It might drop to 45mpg in the winter. The only time I saw under 40mpg on the instant display regularly was climbing the steep hills of Rt 309 on my commute, and when we had the car over 70mph on the interstates. The EPA highway test is like the city; slow and easy going. The top speed is 60mph, so what people think of as highway is really fuel sucking racing in comparison.

The EPA cycles are dated though, and were developed when dynamometers were less capable than today, but it will take Congress to actually have the EPA make new text cycles that reflect modern driving. So the EPA is stuck with coming up with adjustment methods. The ones in 2008 have brought the window sticker numbers in line with what many will actually get. The adjusted 2005 Prius is 45mpg combined. The average reported on Fuelly is 43 to 44 MPG. The average for the gen3 there is around 48mpg to the 50mpg on the sticker. Clarifications and changes to the tests for 2016 and 2017 have refined that further. It will be easier for gen4 owners to beat the EPA.

The EPA test cycles are based on driving patterns in L.A. since they are really CARB's tests, and the patterns are from the '50s. So no real hills, nice weather, and cars didn't have A/C.

The EPA tests aren't ideal, but they are the closest to real world out of all the official ones. That doesn't mean everyone will get those numbers though. It does mean you can compare different models with confidence when deciding on what to buy.

 

EPA test does NOT mimic the center of a major city! Real city driving includes a stop signs at every other corner (0-25mph), AND stop lights on major streets (25-40mph), AND freeways that go from (40-70mph with traffic of wildly varying amounts [think rush hour/bumper to bumper]). Most city people take a bus or train to work and mostly use their cars on weekends for errands, plus an occasional trip to the suburbs, and a rare cross-country road trip. 25ish mpg is rare, but 35ish is not! Suburban(not city) people tend to get better mpgs because they drive further: to and from the city, errands and shopping are far away in other suburbs, with much less traffic.

Very odd that you KNOW FOR CERTAIN that the EPA methods do not account for weather changes, but you do ASSUME that CR includes mixed driving in real-life weather (a very important test, and you want even more tests).

Most consumers would be wise to trust CRs methods and question the EPA's admittedly over-zealous predictions.

 

The EPA city cycle represents driving in L.A. during the 1950's. It is not meant to represent today's crowded city centers, but then it's purpose isn't to get accurate numbers of real world use. It's main is purpose to measure emissions. The fuel economy results came about because somebody figured they could calculate it from the CO2 measurements they were taking.

I know weather doesn't play a role in the EPA tests, because they are perform indoors. I know this because their site said so. I know CR's testing could be affected by weather because their tracks are out side, and they same they also run the highway portion on public roads. I once read they avoid doing tests when it is wet out, but that wasn't mentioned in the link you posted. Since that site didn't comment on temperatures, weather, nor wind, the safe assumption is that they run the tests in whatever the conditions can be in Connecticut.

All the models I've looked into on Fuelly had an average fuel economy from the users close to the EPA combined. Some were higher, some lower. So I think the EPA window sticker hasn't been over-zealous in a decade; they still print your mileage will vary on that window sticker. They test I want to see is an on road one. That is in order to verify somebody isn't cheating on emissions.

But that doesn't matter, because the point of the figures is not to provide results for the real world, but to allow a fair comparison of the fuel economy between different models by testing them under the same conditions. Looking at the EPA numbers, I know which car will get better fuel economy. If you accurately track the fuel economy of your current car, you can make an estimate of what a new car should return for you.

Because they don't control for variables, the CR test results can't be used to compare between models. One car tested in winter, and the other in summer, is not a fair comparison. For an organization that claims to looking out for the consumer, and providing good data for buying decisions, that is a fail

 

Isn't the EPA test performed on a dynamometer? How can that be better than a test track / course test?

 

[QUOTE="But that doesn't matter, because the point of the figures is not to provide results for the real world, ...[/QUOTE]
OK then! Consumer Reports is all about the real world. I understand your point, but most people want/need/deserve to know what mileage their car will actually get in real life, in the real world. EPA was wrong about VW and the Prius. Consumer Reports was right.

 

How do the EPA tests deal with air resistance? In a Prius, when you get above 65mph or so, air resistance is the major source of energy loss. Do they program the equipment with the air resistance profile provided by the manufacturer?

 

When comparing different cars, the variables need to controlled to provide numbers that are honestly comparable. Go outside, and you lose control of some of those variables. Use fuel bought from the corner station, and you lose control of another one. The exact same car is going to give different results under those conditions when tested during different seasons, and maybe even different days. So when a car buyer is looking at those numbers, they can't say how much of the difference between two models is because of them being different cars, or because of those uncontrolled variables.

Consumer Reports was wrong for me, and also wrong for many on Fuelly. And since they don't test emissions, they were fooled by VW like everybody else.

Many don't track the fuel economy of there cars. If they did, they could calculate a decent estimate of what they would get in another car from the EPA numbers. It would be time and cost prohibitive to test cars for all the potential drive cycles people have in the real world.

Air, tire, and drive train resistance are all calculated by coast down tests. Starting at 70mph, the car is allowed to just coast in gear to 20 or 10 MPH. This is done outside, but since the testing is mostly done by the manufacturers, it is done in conditions favorable to them. There is also multiple repeats; tens wouldn't be far fetched. The results get averaged, and entered into the dynamometer as the road load to adjust the resistance of the rollers.

The actual EPA test cycles are also done multiple times, and there are rules on which results can be tossed out or used for the final average. Hyundai fine for the Elantra ratings, likely stemmed from confusion over which results could be used or not. For 2016 model year, the EPA revised the rules for clarification, but also added changes to better reflect real world driving; that coast down test originally started at 50mph.

CR might only run their fuel economy test twice, redo it when those first results are too far apart.

Note: The manufacturer runs the EPA tests. The EPA reviews the work and signs off on it, and they will also run their own tests on some of the models for a given year. They only have the resources to double check about 10% of the models available for a given year. Want then to do more, write your Congress critter to give them more money.

 

Isn't all except air resistance something that would equally be experienced on the dynamometer? How would they isolate the effect of the air resistance?

Thank you for for explanations.

 

LOL! Self testing, now that's a great idea! because big corporations never cheat consumers!

 

I think that the fact that a fraction ARE tested by the government is supposed to deal with that. This is, assuming that there are significant financial penalties if errors in the manufacturer's numbers favoring the manufacturer are found by the random tests.

 

Roll down test

 

Different engines, transmissions, and tires are have different levels of friction. Wind tunnels are expensive. Theses resistances are all measured together because it is the simplest way, and there is no advantage to having separate ones for the test.

Which is why it is important to have published testing procedures. So that their results can be verified by outside sources, like the EPA. Not publishing their method means we can't double check CR's results. If the testers favor one brand, or dislike a model, they could be testing in a manner that will influence the results, and no one would be able to prove it.

Hyundai and Kia paid $100 million in civil penalties for their inflated MPG numbers.
Hyundai and Kia Clean Air Act Settlement | Enforcement | US EPA
The fine is something like $30k to $40k per car sold under the erroneous/cheating values.

 

"But that doesn't matter, because the point of the figures is not to provide results for the real world ..."

OK then! Consumer Reports is all about the real world. I understand your point, but most people want/need/deserve to know what mileage their car will actually get in real life, in the real world. EPA was wrong about VW and the Prius. Consumer Reports was right.

"Which is why it is important to have published testing procedures. So that their results can be verified by outside sources, like the EPA. Not publishing their method means we can't double check CR's results. If the testers favor one brand, or dislike a model, they could be testing in a manner that will influence the results, and no one would be able to prove it."

And this is why is so important that Consumer Reports keeps their tests secret. Publishing the EPA procedure with "self testing" is exactly how Volkswagen cheated so many, and so long:
The tech behind how Volkswagen tricked emissions tests - The Washington Post

 

It depends how it is driven and in what conditions.

The CR test is unlikely to represent any random driver much better than any other test.
All you are saying is that YOU drive like the CR test. I don't.

 

You not liking/trusting/knowing-it-all doesn't make the time tested CR test methodology any less than the most accurate tests available. Consumer Reports highly scientific tests are on done using more than the single, flawed EPA machine. They are performed inside and outside. Using a testing track AND on real roads with real weather and take much longer and have proven statistically to be more accurate than the EPAs quickie and repeatedly wrong and cheated, "self-tests". The EPA has gotten better every 12 years (their glacially slow update cycle), but they openly admit still overestimate most drivers' mpgs by 10%! This isn't complicated.

 

Source?

We have ready access to the EPA data going back over a decade: www.fueleconomy.gov

Actually thanks to CARB and the EPA, they figured out the VW scam resulting in billions of dollars of fines and penalties for VW. VW/Bosch was tempted to cheat but when caught, the crime has had and continues to have real penalties. In effect, the cheat killed VW/Audi diesel sales in the USA and there are EU countries planning to ban them.

In contrast, Consumer Reports was a follower, not a leader in hunting down this scandal. Of course you are welcome to cite when and what they did. After all, I had already dropped our subscription but the open press wasn't citing Consumer Reports as sourcing anything in the scandal: VW Faces $17B Fine for Emissions Scam | PriusChat

Bob Wilson

 

Nothing to do with liking/trusting/knowing whatever.

Read my post again.

 

Actually no. Self-policing and the EPA failed. Complete and total failure. Took an investigating NGO to find it:

“We’re a tiny, non-governmental organization,” Drew Kodjak, executive director of the International Council for Clean Transportation, said in an interview Wednesday. “It was really happenstance that this was ultimately uncovered.”

In 2013, his organization commissioned a study of VW diesels by West Virginia University after questions were raised about European diesel emissions standards and whether European vehicles were emitting too much nitrogen oxides linked to smog.
How VW got caught cheating emissions tests

How Volkswagen Got Caught Cheating Emissions Tests By A Clean Air NGO | IFLScience
Volkswagen Diesel Emissions Scandal - Consumer Reports
Are Volkswagen’s media vehicles the same as what you can buy?

 

Then we'll have to agree to disagree. Although the NGOs informed CARB/EPA, they had as much legal standing as Consumer Reports ... none at all. The crime was not revealing the defeat device.

CARB/EPA had the legal standing and once revealed whacked VW/Audi with an expensive clue by four.

I'll be more impressed with CR when they are parties to judicial remedies.

Bob Wilson