Was any other car company gaming emission standards?

As most of you already know, Volkswagen was recently caught cheating on emission tests. But were they really alone in doing so? The EPA data shows some suspicious patterns.

Without getting too technical (in any case, the specifics are still unclear), there's a tradeoff between fuel efficiency, and NOx emissions. So for a given level of performance, the software that controls a modern diesel engine can be tuned so that it is more fuel efficient, but produces more NOx, or it can be tuned so that it is less fuel efficient, but produces less NOx.

Since Volkswagen had problems meeting the NOx standards in the US, they decided to introduce software that detected when an emission test was being performed, and tuned the engine so as to decrease NOx production, in the process potentially worsening fuel economy relative to regular driving conditions.

One possible outcome of this procedure is that the cars involved might actually have better fuel economy in real life conditions, than during testing. For example the Diesel version of the Jetta was famous for this.

Since I happened to have the EPA mileage data lying around my hard-drive from a different project (you can get your copy here), and since I knew that fuelly.com  logged real world mileage performance, I thought it would be interesting to see if this pattern was systematic. Indeed, all of the affected VW models seemed to get between 10% and 20% more miles to the gallon than what their EPA Combined mileage rating would suggest.

Do any other models show a similar pattern? The Disesel version of the Chevrolet Cruze stands out. In fact it shows 20% better mileage on the road than in the tests, more than any other model. Several Mercedes-Benz models stand out as well, but there a very few observations in the fuelly.com dataset for these, so it is hard to draw inference from these.


Another possible explanation for this pattern is sample selection. Since the fuelly.com is not a random sample (users have to download an app), it is likely that their user base is more fuel conscious than the average driver. Also, the combined rating is calculated by the EPA by taking a 55/45 weighted average of the City and Highway tests. If owners of diesel cars spend much more time on highways than regular drivers, it is entirely possible that the observed mileage is simply a product of their driving habits. Nonetheless, owners of other Diesel models don't seem to show this pattern.

To address this concern I calculated what fraction of their driving the users of each model would have had to do on highways, to obtain the observed mileage. In the case of the diesel Cruze, it is 68%.

I briefly thought of buying some out of the money puts on GM with a friend, but the fees were too expensive relative to our limited investment funds. As a result, I can confirm that I have no financial conflict of interest in the matter.

Comments

  1. This was huge information for all ,those who needed these type article. This was really good and of course knowledgeable for Volkswagen ID6. Thank you for sharing this much information with us

    ReplyDelete
  2. You have done good work by publishing this article here.ev charger I found this article too much informative, and also it is beneficial to enhance our knowledge. Grateful to you for sharing an article like this.

    ReplyDelete

  3. Ruger SP101 Revolver. The SP101 was a small, lightweight frame revolver based on the company's reputation for robust and reliable firearms.Beretta USA 3032 Tomcat

    ReplyDelete
  4. I really love this list, but I would really appreciate it if you can add some sites to build backlinks for an education niche blog, thanks in advance very helpful full post ammunition online sales I had not heard the phrase LSI before, so I appropriate the information shared. Help total blog lots of information about it. Thank you admin for providing this information.

    ReplyDelete
  5. All in one solution for the SEO, Thank you so much for sharing, it’s very helpful and you own one of the best on the internet. TESTIMONIALSThanks for sharing! please keep it up Maintains!

    ReplyDelete
  6. Pretty good post. I just stumbled upon your blog and wanted to say that I have really enjoyed reading your blog posts. Anyway,Brown Bear, 7.62×39, Blank Ammo, 240 Rounds I'll be subscribing to your feed and I hope you post again soon. Big thanks for the helpful info.

    ReplyDelete
  7. Thank you a lot for giving everyone remarkably special chance to discover important secrets from here. It is usually so ideal and as well , packed with a good time for me personally and my office acquaintances to visit your website no less than 3 times per week to study the fresh issues you will have. And lastly,Brown Bear, 7.62×39, Blank Ammo, 240 Rounds I’m also certainly amazed considering the sensational techniques you serve. Certain 1 points in this posting are in reality the most suitable I’ve had.

    ReplyDelete
  8. All in one solution for the SEO, Thank you so much for sharing, it’s very helpful and you own one of the best on the internet. Lexi Thanks for sharing! please keep it up Maintains!

    ReplyDelete
  9. I was checking continuously this list and I’m impressed! Extremely useful info especially this blog commenting sites list. bob Thank you and best of luck.

    ReplyDelete
  10. Your information is great. It’s beneficial for this blog. Also, great with all of the valuable information you have. Keep up the excellent work you are doing well. honey thank you

    ReplyDelete
  11. Hello Sir! Thanks for providing a great informative and beautiful-looking blog. Kona Really nice required information & the things I never imagined and I would request, write more blogs and blog posts like that for us. Thanks for sharing!

    ReplyDelete
  12. Hello Sir! We’re new to blogging as our primary source of income has always been freelance software engineering. Fiocchi High Velocity Ammunition 28 Gauge Also great with all of the valuable information you have. Keep up the excellent work you are doing well.

    ReplyDelete
  13. Usually, I do not learn to post on blogs, however I would like to say that this write-up very compelled Wolf .45 ACP Ammo me to take a look at and do it! Your writing taste has amazed me. Thanks, quite a nice post.

    ReplyDelete

Post a Comment

Popular posts from this blog

Now, that's a disclaimer paragraph!

What Genghis Khan, but Elizabeth Can't