Dieselgate and CO2 emissions

In case you’ve been living under a rock, Volkswagen was caught cheating on emissions testing with their 2009-2016 diesels. Recently, a proposed settlement including a buyback program (as well as, potentially, a fix) has been announced for the 2009-2015 2.0 liter vehicles. One concern, however, is the CO2 emissions impact of this buyback – both in terms of manufacturing emissions, and in terms of fuel consumption.

For manufacturing emissions, it’s worth reading this report from Argonne National Laboratory, best summarized as saying that the car will have been responsible for up to about 2000 kg of CO2 emissions during manufacturing. A replacement vehicle, if it’s a hybrid, plug-in hybrid, or battery electric vehicle, could result in significantly more emissions – up to about 3200 kg.

As far as CO2 emissions that the vehicle produces while in service, however… seeing as this is in the US, almost all of the replacement vehicles that are available (outside of battery electric vehicles) will be gasoline-fueled. It’s worth noting, however, that the increased energy density of diesel fuel is part of what contributes to the reduced fuel consumption of diesel vehicles, and the increased energy density results in proportionately higher CO2 emissions – 13.95% higher emissions, actually a little more than what’s proportionate. However, while the EPA has a formula for determining gasoline equivalent energy for electric vehicles (using a baseline of 115,000 BTU per gallon for gasoline), they haven’t applied such a formula to diesel (which, per the Alternative Fuels Data Center, has 128,488 BTU/gal, or 11.73% of the energy).

Therefore, I’ve decided to compile a list of the affected 2.0 liter TDIs, using the fuel economy from the EPA’s fuel economy data files, and the gasoline fuel economy required to match the CO2 emissions, to help people decide whether to keep and fix their car (keep in mind that fuel economy will probably be reduced by any fix, so the reputation that TDIs have of beating their EPA fuel economy may not continue), or to go ahead with the buyback and purchase a replacement. All figures will be reported in miles per US gallon (for 2012+, where unrounded numbers are available, to three significant figures) so that it’s easier for most people to read, but the math is being done in gallons per 100 miles, so it will accurately reflect fuel consumption and resulting CO2 emissions. (Doing the math in miles per US gallon will result in misleading results, as my previous blog post discusses.)

If you don’t want to read the table, here’s a summary of the best and worst cars.

The best TDI for gasoline CO2-equivalent fuel economy is the 2015 Jetta with a DSG, at a gasoline CO2 equivalent of 27.6 city, 31.8 combined, and 39.2 highway, but the best highway figure is a manual Jetta, at 40.1 highway. The worst of the 2015s is the Beetle Convertible with a manual, at a gasoline CO2 equivalent of 26.0 city, 29.5 combined, and 35.3 highway.

Excluding 2015s (which got a lot more efficient for the most part), the best is the 2012-2014 Passat with a manual, at an equivalent of 27.0 city, 30.9 combined, and 37.4 highway. The worst overall is the 2013-2014 Beetle Convertible with a DSG, at an equivalent of 24.6 city, 31.3 combined, and 32.1 highway, although the manual got 24.4 gasoline CO2 equivalent city.

The full table with diesel MPG per the EPA, and gasoline CO2 equivalent MPG follows.

2009:

Model Transmission City Comb Hwy Gas City Gas Comb Gas Hwy
Jetta Manual 30 34 41 26 30 36
Jetta DSG 29 33 40 25 29 35
SportWagen Manual 30 34 41 26 30 36
SportWagen DSG 29 33 40 25 29 35

2010:

Model Transmission City Comb Hwy Gas City Gas Comb Gas Hwy
A3 DSG 30 34 42 26 30 37
Golf Manual 30 34 41 26 30 36
Golf DSG 30 34 42 26 30 37
Jetta Manual 30 34 41 26 30 36
Jetta DSG 30 34 42 26 30 37
SportWagen Manual 30 34 41 26 30 36
SportWagen DSG 30 34 42 26 30 37

2011:

Model Transmission City Comb Hwy Gas City Gas Comb Gas Hwy
A3 DSG 30 34 42 26 30 37
Golf Manual 30 34 42 26 30 37
Golf DSG 30 34 42 26 30 37
Jetta Manual 30 34 42 26 30 37
Jetta DSG 30 34 42 26 30 37
SportWagen Manual 30 34 42 26 30 37
SportWagen DSG 29 33 39 25 29 34

2012:

Model Transmission City Comb Hwy Gas City Gas Comb Gas Hwy
A3 DSG 29.8 34.2 41.5 26.2 30.0 36.4
Golf Manual 29.7 34.2 41.9 26.1 30.0 36.8
Golf DSG 29.8 34.2 41.5 26.2 30.0 36.4
Jetta Manual 29.7 34.2 41.9 26.1 30.0 36.8
Jetta DSG 29.8 34.2 41.5 26.2 30.0 36.4
Passat Manual 30.8 35.2 42.6 27.0 30.9 37.4
Passat DSG 30.5 34.2 40.2 26.7 30.0 35.3
SportWagen Manual 29.7 34.2 41.9 26.1 30.0 36.8
SportWagen DSG 28.9 34.2 39.5 25.3 30.0 34.6

2013/2014 (A3 only for 2013):

Model Transmission City Comb Hwy Gas City Gas Comb Gas Hwy
A3 DSG 29.9 34.2 41.5 26.2 30.0 36.4
Beetle Manual 27.8 32.4 40.7 24.4 28.5 35.7
Beetle DSG 28.6 32.5 38.9 25.1 28.5 34.1
Beetle Conv Manual 27.8 32.4 40.7 24.4 28.5 35.7
Beetle Conv DSG 28.0 31.3 36.6 24.6 27.5 32.1
Golf Manual 29.6 34.1 41.9 26.0 29.9 36.7
Golf DSG 29.9 34.2 41.5 26.2 30.0 36.4
Jetta Manual 29.6 34.1 41.9 26.0 29.9 36.7
Jetta DSG 29.9 34.2 41.5 26.2 30.0 36.4
Passat Manual 30.8 35.2 42.6 27.0 30.9 37.4
Passat DSG 30.5 34.2 40.2 26.7 30.0 35.3
SportWagen Manual 29.6 34.1 41.9 26.0 29.9 36.7
SportWagen DSG 28.9 34.2 39.5 25.3 30.0 34.6

(Note: the Golf and Jetta DSGs have slightly different mileage in the unrounded figures for 2014 (the removal of the A3 probably made them have to slightly re-rate them, as they shared the A3’s testing), but rounded to three significant figures, the difference is not noticeable.)

2015:

Model Transmission City Comb Hwy Gas City Gas Comb Gas Hwy
A3 DSG 31.2 35.6 43.0 27.4 31.2 37.8
Beetle Manual 30.5 34.3 40.5 26.8 30.1 35.6
Beetle DSG 30.7 34.4 40.5 26.9 30.2 35.6
Beetle Conv Manual 29.6 33.6 40.1 26.0 29.5 35.3
Beetle Conv DSG 30.3 33.9 39.7 26.6 29.8 34.8
Golf Manual 30.4 35.6 44.9 26.7 31.3 39.4
Golf DSG 31.2 35.6 43.0 27.4 31.2 37.8
Jetta Manual 30.7 36.0 45.7 26.9 31.6 40.1
Jetta DSG 31.4 36.3 44.7 27.6 31.8 39.2
Passat Manual 29.8 34.8 43.6 26.2 30.5 38.2
Passat DSG 29.6 34.1 41.9 26.0 29.9 36.8
SportWagen Manual 30.7 35.3 43.3 26.9 31.0 38.0
SportWagen DSG 31.2 35.3 41.9 27.4 30.9 36.8

2 comments on “Dieselgate and CO2 emissions

  1. Excellent but I’m a little confused. Do we need to see new EPA metrics for the “fixed” diesels?

    Speaking for myself, I’ve never been terribly interested in the CO{2} emissions but you bring up a good point that there should be simple CO{2} rate to MPG or 100 mi/L based on gasoline, ethanol, and diesel. The EPA uses ‘standard’ fuels so the chemical compositions should be close enough to make linear terms.

    Again, speaking for myself, I was a critic of the CNW Marketing “Dust-to-Dust” report for the obvious ‘vehicle life-time mileage’ errors. But there were claims about manufacturing costs that continue to bother me because they are so difficult to independently quantify. Again, legacy from the “Dust-to-Dust” report that was supported by the “Alliance of Automotive Manufacturers.”

    I’m OK with things individuals can test and verify but it is too easy to get fudged numbers about manufacturing costs either in dollars or CO{2} emissions. For example, the hybrid skeptics often repeat about ‘shipping nickel from Canada to Europe to China.’ But the obvious is shipping has a rate per ton and nickel ore and processed products are just another commodity.

    I appreciate the effort even if like many USA readers, perhaps not so CO{2} focused.

    • So, I’m using the mileage that the cheating TDIs got on the EPA tests for a reason – that reason being that they weren’t cheating during the test. Therefore, that should be reasonably representative of their fuel efficiency after the fixes are performed, I’d guess. (Note the reputation for beating their EPA MPG right now – they beat it when they’re cheating.)

      It is worth noting that fueleconomy.gov actually does show CO2 numbers based on the combined MPG, in the Energy and Environment tab – both tailpipe CO2 and upstream GHG – an example of that here.

      And, yes, manufacturing emissions are pretty much a wild-ass guess by anyone, but there’s a reason I used Argonne’s numbers for that – the vast majority of Argonne’s funding comes from the US Department of Energy, whose vested interest is efficient and safe energy supply, not selling gas guzzlers. $617,603M of their $737,701M budget came from the Department of Energy (the rest being a mix of the Department of Homeland Security, and work for “others” (their graph doesn’t break this down, so I’m not sure if it’s governmental or not)). In any case, that discussion wasn’t the main point of my article, but it biases things even more towards hybrids – that if your priority is CO2, you want to get out of your VW diesel ASAP and replace it with an efficient gasoline vehicle (and it doesn’t even necessarily need to be a hybrid to beat it on CO2 emissions, but that helps, and makes the CO2 payoff period short, despite the increased manufacturing emissions that Argonne found).

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