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I think this doesn't take into account the reasons behind this (in the UK at least, where I live). Tax cuts were made because CO2 emissions were viewed as bein

I think this doesn't take into account the reasons behind this (in the UK at least, where I live). Tax cuts were made because CO2 emissions were viewed as being the problem, and Diesels are more fuel efficient than an equivalent-power petrol engine, hence lower CO2 emissions. It wasn't that the regulators were 'picking winners from specific technologies' as you claim, but they were favouring any vehicle with a low CO2 emission per kilometer. If that was achievable by a petrol car, then it was rewarded; low emission petrol cars got the same break, but they're inherently less efficient due to the lower compression ratio of a petrol engine.

donjoe 7y ago
... whereas less CO2 emissions caused by Diesel engines is a misconception, too. Diesel comes with a higher energy density which means there are more CO2 emissions per burned liter of Diesel in comparison to gas. Burning a liter of Diesel emits 2.6kg of CO2, gas 'only' emits 2.3kg of CO2 [1]. Plus, a Diesel engine is heavier compared to a gas engine with comparable specs. [1] https://www1.wdr.de/wissen/technik/kohlenstoffdioxid-sprit-100.html https://www1.wdr.de/wissen/technik/kohlenstoffdioxid-sprit-1...
- scythe 7y ago
  This comparison is wrong. You want CO2 per distance, not CO2 per liter. From these numbers if it could go either way. If the diesel engine gets 10% more distance/liter then it's worse than an Otto engine, but if it gets 20% more distance/liter then it's cleaner than an Otto engine. CO2/liter tells us very little. However, what is certain is that the CO2 savings from diesel is small and certainly less than 50%. That's not going to get us where we need to go in terms of carbon emissions.
  - donjoe 7y ago
    I wouldn't say it's per se wrong. The tax is based on a per liter basis and not on a per distance/liter basis. If you'd want to tax CO2 emissions, Diesel would need a higher tax rate than gas since it'll emit more CO2 per burned liter.
    - girvo 7y ago
      While it's been a while since I lived there, I'm reasonably sure that in New Zealand, Diesel is indeed taxed at a rather higher rate.
hannob 7y ago
> Diesels are more fuel efficient than an equivalent-power petrol engine, hence lower CO2 emissions. > but they were favouring any vehicle with a low CO2 emission per kilometer You're making two statements here which sound like they're more or less the same, but they aren't. The first is true, the second is not. An equivalent-power diesel car produces less CO2. But they aren't equivalent. The tax breaks and lower fuel use led to bigger cars. On average Diesel cars have higher CO2 emissions per kilometer.
- djaychela 7y ago
  >On average Diesel cars have higher CO2 emissions per kilometer. I don't think that's true (in the UK at least) - both in that it's vanishingly rare to find a petrol vehicle that fit into the lowest 5 UK tax brackets (which are g/km of CO2) - and also in terms of real-world fuel use. I've owned probably 70 cars in the last 10 years or so (I buy and sell as a side gig), and all of the diesels have had lower fuel use for equivalent performance. They tend to be 'one size bigger' in terms of engine (so, say a 1.9 instead of a 1.6, or a 1.4 instead of a 1.1), but even taking that into account they will be a 10-20 mpg better on fuel, with a petrol 1.4 focus giving maybe 30 mpg average, and a diesel (1.6) one easily making 45-50 mpg, more on a run. And that means lower CO2 emissions. Yeah, you might see the occasional stupidly large diesel car/chelsea tractor, but most of them are 1.9D VAG, and 1.6 or 2.0 Peugeot/Citroen/Ford HDI/TDCIs - there are hundreds of thousands of them out there on the roads.
  - AstralStorm 7y ago
    Compared to 0.7 through 1.4l petrol cars, the diesel numbers are less than impressive and still bigger. And the 1.4 can easily can have horsepower and acceleration exceeding a 2.1l diesel.
- usrusr 7y ago
  > The tax breaks and lower fuel use led to bigger cars. We don't know that. Diesel is far more prevalent with bigger cars because they tend to eat through more energy over their lifetime, making it more likely to break even on the up-front premium for diesel (not just more joule per kilometre, but typically also far more kilometres per year). But chances are that without diesel, cars in Europe would be just as big today (e.g. they still tend to be smaller that in a certain famously petrol-centric country)

donjoe 7y ago

... whereas less CO2 emissions caused by Diesel engines is a misconception, too. Diesel comes with a higher energy density which means there are more CO2 emissions per burned liter of Diesel in comparison to gas. Burning a liter of Diesel emits 2.6kg of CO2, gas 'only' emits 2.3kg of CO2 [1]. Plus, a Diesel engine is heavier compared to a gas engine with comparable specs. [1] https://www1.wdr.de/wissen/technik/kohlenstoffdioxid-sprit-100.html https://www1.wdr.de/wissen/technik/kohlenstoffdioxid-sprit-1...

scythe 7y ago
This comparison is wrong. You want CO2 per distance, not CO2 per liter. From these numbers if it could go either way. If the diesel engine gets 10% more distance/liter then it's worse than an Otto engine, but if it gets 20% more distance/liter then it's cleaner than an Otto engine. CO2/liter tells us very little. However, what is certain is that the CO2 savings from diesel is small and certainly less than 50%. That's not going to get us where we need to go in terms of carbon emissions.
- donjoe 7y ago
  I wouldn't say it's per se wrong. The tax is based on a per liter basis and not on a per distance/liter basis. If you'd want to tax CO2 emissions, Diesel would need a higher tax rate than gas since it'll emit more CO2 per burned liter.
  - girvo 7y ago
    While it's been a while since I lived there, I'm reasonably sure that in New Zealand, Diesel is indeed taxed at a rather higher rate.

hannob 7y ago

> Diesels are more fuel efficient than an equivalent-power petrol engine, hence lower CO2 emissions. > but they were favouring any vehicle with a low CO2 emission per kilometer You're making two statements here which sound like they're more or less the same, but they aren't. The first is true, the second is not. An equivalent-power diesel car produces less CO2. But they aren't equivalent. The tax breaks and lower fuel use led to bigger cars. On average Diesel cars have higher CO2 emissions per kilometer.

djaychela 7y ago
>On average Diesel cars have higher CO2 emissions per kilometer. I don't think that's true (in the UK at least) - both in that it's vanishingly rare to find a petrol vehicle that fit into the lowest 5 UK tax brackets (which are g/km of CO2) - and also in terms of real-world fuel use. I've owned probably 70 cars in the last 10 years or so (I buy and sell as a side gig), and all of the diesels have had lower fuel use for equivalent performance. They tend to be 'one size bigger' in terms of engine (so, say a 1.9 instead of a 1.6, or a 1.4 instead of a 1.1), but even taking that into account they will be a 10-20 mpg better on fuel, with a petrol 1.4 focus giving maybe 30 mpg average, and a diesel (1.6) one easily making 45-50 mpg, more on a run. And that means lower CO2 emissions. Yeah, you might see the occasional stupidly large diesel car/chelsea tractor, but most of them are 1.9D VAG, and 1.6 or 2.0 Peugeot/Citroen/Ford HDI/TDCIs - there are hundreds of thousands of them out there on the roads.
- AstralStorm 7y ago
  Compared to 0.7 through 1.4l petrol cars, the diesel numbers are less than impressive and still bigger. And the 1.4 can easily can have horsepower and acceleration exceeding a 2.1l diesel.
usrusr 7y ago
> The tax breaks and lower fuel use led to bigger cars. We don't know that. Diesel is far more prevalent with bigger cars because they tend to eat through more energy over their lifetime, making it more likely to break even on the up-front premium for diesel (not just more joule per kilometre, but typically also far more kilometres per year). But chances are that without diesel, cars in Europe would be just as big today (e.g. they still tend to be smaller that in a certain famously petrol-centric country)