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A recent YouTube video features a claim that the VW Passat TDI 1.6 and similar cars have been banned by the US government, specifically because their gas mileage is too high. The purported reasoning is that if many people bought these cars, the government would lose revenue on gas taxes.

Could Volkswagen sell the Passat TDI 1.6 in the US if it wanted to? If not, what laws prohibit it? Does the US systematically ban high-gas-mileage cars?

(I find myself completely uninformed about the US auto market and vehicle regulations, but I'm also psychologically biased against the claim and so don't trust my own research very strongly.)

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    I don't have references right now, but the answer is: Not exactly. The U.S. has strict emissions laws that make many high-efficiency engines (especially diesel ones) illegal to operate in the U.S. However, it's the emissions of these engines, not the efficiency, that is illegal. Compliance with U.S. emissions laws often requires reducing the efficiency for various complex reasons. – Flimzy May 7 '12 at 22:27
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    The true reasons behind these laws are matters for speculation. I think the more credible conspiracy theories relate to oil companies lobbying lawmakers in the name of "environmental protection," but with a hidden agenda of increased oil consumption, rather than a gov't goal of increasing tax revenue (the easy way to increase tax revenue is to raise taxes). But the are just that: conspiracy theories, and pretty impossible to prove. – Flimzy May 7 '12 at 22:30
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    Given how low US taxes on fuel are, I can't see the theory holding up: governments just don't make enough on the tax to make stupid laws worth it. Whether US emission laws are sensible is another issue. – matt_black May 7 '12 at 22:35
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    @ratchetfreak: There are multiple laws at play, but the most recent one (apparently from CA only) limits diesel particulate matter in the exhaust. To combat this, manufacturers install DPFs (diesel particulate filter) in the exhaust line, which limits exhaust flow, which in turn limits engine output. There are other rules, too, which require more complex/less efficient engines and/or engine tuning, for the "benefit" of less/more favorable emissions. – Flimzy May 8 '12 at 2:31
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    BTW, in video comments ppl seem to compare UK mpg with US mpg without realizing that imperial gallon (4.5L) is significantly larger than US gallon (3.8L). – vartec May 8 '12 at 11:27
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There is no law in the US that bans high gas mileage cars. In fact under Corporate Average Fuel Economy (CAFE) regulations manufacturers are fined for producing low gas mileage cars.

There are however regulations that place strict limits on the emissions produced by cars (note - Californian regulations but also used by many other states).

LEV II Exhaust Mass Emission Standards

The emissions for the VW Passat 1.6 TDI sold in the UK are as follows (source):

VOLKSWAGEN Passat Saloon 1.6 CR TDI

Converting the above data from mg/km to g/mi gives CO Emissions of 0.267 g/mi and NOx Emissions of 0.166 g/mi. So the VW Passat 1.6 TDI can not be sold in any state using the Californian regulations as it emits too much NOx.

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    Chemical engineer here. For internal combustion engines: all other things being equal, the hotter an engine can comfortably run, the higher its efficiency. NOx is produced under conditions of high pressure and temperature. NOx emissions can be reduced by cooling the combustion temperature (reducing efficiency). California is particularly strict on NOx emissions, for some pretty good reasons; next time you're in LA, look up to see them. A lot of that brown stuff in the sky is from NOx. So it's not terribly surprising that fuel efficient cars and California don't mix well. – Jason Jun 27 '17 at 8:01

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