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Study: Some car models consuming around 50% more fuel than official results

transportenvironment.org

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Re: Study: Some car models consuming around 50% more fuel than official results

#221

Post by henningo »

I think it is a bit unfair to just blame the manufacturers. The legislation could likely be changed to make for a more robust test approach. After all, it is engineers we are talking about here, if they are given a task to optimize an engine's emissions and fuel consumption to a specific drive cycle they will do it. But then of course you have the ethical aspects which I won't go into.

A computer science analogy to this would be if I gave you an uncompressed image and you had to develop a compression algorithm that made the image as small as possible, you could likely come up with a really good solution. But your algorithm most likely wouldn't do as well on any other image.

I think that a feasible solution to this will be to test under a wider range of conditions and add (statistically defined) noise to the testing procedures. The added cost of additional testing would be very small in comparison to the cost of a vehicle development program.

A good overview of the different drive cycles can be found here: http://www.car-engineer.com/the-different-driving-cycles/

Re: Study: Some car models consuming around 50% more fuel than official results

#222

Post by acomjean »

Wait a second..

When I bought my car (10 years ago) and read reviews, a lot of them say here's what the epa said you'd get for mileage, and heres what we actually got. There is always a difference (maybe 10%). But if it claims 30 mpg and you are getting 17 , I like to think more than few people might notice.

Part of the reason VW was accused of cheating on emissions was it helped mileage.

edit: as pointed out, its 50% more fuel... But still a noticeable difference..

Re: Study: Some car models consuming around 50% more fuel than official results

#223

Post by alkonaut »

bengoodger wrote: post #104
alkonaut wrote: post #42

The thing is that the cheats (throwing out unnecessary weight, taping door gaps etc, using super hard notrogen inflated tyres, etc.) would add a constant amount to the fuel consumption, say .2 liter per 10km. If you keep pushing your engine consumption downwards to the ridiculous levels we see now ( Just goes to show that the cars should be designed without large door gaps or outside mirrors (cameras instead) and so…

The lack of good data is really frustrating. The EPA adjusted the formula for mileage a few years ago which made things slightly better but I never come close to hitting the results in my car. Observed economy is related to personal circumstances, and in my case living at 700 elevation and traveling down close to 0 on a daily basis hurts my scores (along with tire lifetimes, etc). Another thing that bothers me is tha…

Yeah I wouldn't trust some forum user either, but certainly some of the larger magazines that do long real life tests of cars.

Re: Study: Some car models consuming around 50% more fuel than official results

#224

Post by arasmussen »

acomjean wrote: post #222

Wait a second.. When I bought my car (10 years ago) and read reviews, a lot of them say here's what the epa said you'd get for mileage, and heres what we actually got. There is always a difference (maybe 10%). But if it claims 30 mpg and you are getting 17 , I like to think more than few people might notice. Part of the reason VW was accused of cheating on emissions was it helped mileage. edit: as pointed out, its 50…

50% more fuel than official results would be like claims 30 mpg and actually getting 22.5 mpg.

Re: Study: Some car models consuming around 50% more fuel than official results

#225

Post by number_six »

tremon wrote: post #152
Zelphyr wrote: post #102

Earlier quoted context omitted.

Care to share some of those tips?

This is by no means an exhaustive list, nor an authoritative one. Would love to hear other's thoughts on these: - When accelerating, try not to over-extend the throttle. If the engine is at 2k rpm, you get just as much acceleration from 30% throttle as 100%, at half the fuel cost. - Release the throttle well before you reach a traffic light/stop sign. Deceleration by engine will cause a smoother stop and gives the tr…

I have a CVT transmission and while I'm sure it is very smart I still feel like I could do better with a manual. I don;t like my car vey much, but it is too practical and cheap to change.

Re: Study: Some car models consuming around 50% more fuel than official results

#226

Post by zardo »

happyscrappy wrote: post #85
maxerickson wrote: post #78

Earlier quoted context omitted.

Europe generally has more stringent regulation and worse pollution than the US. It's many more people in a smaller space. Noise isn't a good predictor though, a muffler is a drain on efficiency.

Actually the VWs that were emitting 40x pollution in the US were only 10x of the Euro regs.

Eu has stricter PM limits, the US has stricter NOx limits.

Re: Study: Some car models consuming around 50% more fuel than official results

#227

Post by rtkwe »

dragonwriter wrote: post #218
rtkwe wrote: post #217

Earlier quoted context omitted.

In the US the EPA confirms the MPG ratings for 10%-15% of vehicles and has prescribed (edit: prescribed vs proscribed) testing regimes for each of the estimates. The issue isn't with manufacturers lying so much as the test schedule laid out by the EPA just doesn't reflect how people drive.

Nitpick, but "prescribed"; is pretty much the opposite of "proscribed".

Whoops. Serves me right for writing comments 3 words at a time between Sametime pings...

Re: Study: Some car models consuming around 50% more fuel than official results

#228

Post by mod »

enraged_camel wrote: post #193
ticktocktick wrote: post #103

Earlier quoted context omitted.

Just stay off the brakes as much as possible. No big secret really.

Unless your car has regenerative breaks, in which case you should randomly and unpredictably break to generate free energy. edit: downvoters are once again proving that HN doesn't get jokes.

I think it's more that HN doesn't appreciate jokes, the discussion tends away from that here.

Also, from the guidelines:

Please resist commenting about being downvoted. It never does any good, and it makes boring reading.

Re: Study: Some car models consuming around 50% more fuel than official results

#229

Post by rnovak »

kbenson wrote: post #212
vkjv wrote: post #86

Earlier quoted context omitted.

I thought the same. In my anecdotal experience, drivers tend to get much lower than the manufacturer mileage because they optimize for things other than fuel economy (e.g., speed). My dad taught me lots of tips on conserving fuel and thankfully I've exceeded the sticker numbers on every car I've owned.

But that's actually irrelevant for the cited report. What the referenced graph says is that from 2008 to 2014, auto manufacturers declared a certain increase in emissions/economy, real world people reported a different amount, and those amounted to, unique to GM in this report, a negative percentage in how well they achieved their claims. That is, on average, GM car fuel economy got worse over this period, or people'…

It's not irrelevant at all.

Manufacturers report fuel consumption during a controlled environment, with specific driving habits, etc.

Real world people drive insane (at least in the US), and most wouldn't even re-pass their drivers-license test, so most assuredly do not have the best driving habits.

So drawing the conclusion that manufacturers are "lying" from the discrepancies between those two data sets is ridiculous.

Re: Study: Some car models consuming around 50% more fuel than official results

#230

Post by acomjean »

arasmussen wrote: post #224
acomjean wrote: post #222

Wait a second.. When I bought my car (10 years ago) and read reviews, a lot of them say here's what the epa said you'd get for mileage, and heres what we actually got. There is always a difference (maybe 10%). But if it claims 30 mpg and you are getting 17 , I like to think more than few people might notice. Part of the reason VW was accused of cheating on emissions was it helped mileage. edit: as pointed out, its 50…

50% more fuel than official results would be like claims 30 mpg and actually getting 22.5 mpg.

Fair enough.. But still a significant real world difference.

EPA (USA) tests aren't really real world and they don't just drive the cars. Well they drive them on a dyno on a preset pattern (see the picture in the link).

https://www.fueleconomy.gov/feg/how_tested.shtml

they measure emissions to estimate fuel consumption.

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