On the show Real Time with Bill Maher (Jan 9, 2015), Jay Leno (a guy that seems knowledgeable about cars) made this very interesting statement 37 minutes in:

A 1977 Ford Galaxy, one of those big ones. Park it on the street, with the engine off...pollutes more than a Ford Fusion going down the road at 60 miles an hour.[...]Because A) the gas tank is [unclear part] vented, closed, so it just goes to atmosphere. The plastic used, ever notice old cars when they sit in the sun, the windshield gets all clouded up, and it's grease because it's gas, it's toxic gas, coming off the plastics and the oil used to make that. They don't use any of that anymore.

Transcription was made by myself so you'll have to bear with it. We could probably compare a car from the 70s versus a recent one.

Does anyone have any source for such a statement? Maybe some numbers backing this statement. I assume that Jay Leno didn't consider the manufacturing of the new car or the recycling of the old one, so that part can be ignored. I would assume one could only consider atmospheric pollution.

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    What he's referring to in A) is the evaporative emissions. EVAP controls weren't required nationally until 1978 (page 7) (I think California required it in 1971), so any gasoline that evaporated in the tank would just vent to the atmosphere. Nowadays, it's captured in a charcoal canister, then vented into the fuel system when the vehicles is running. EVAP emissions are considerable (10-20% of total emissions absent control), but I have no idea how they compare to modern total emissions. – Compro01 Jan 16 '15 at 0:25
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    I can't see how this could be answered. Is evaporated fuel and plastic fumes better or worse than CO2/NO2/rubber particles etc.? Seems opinion-based, no? – Oddthinking Jan 16 '15 at 0:59
  • @Oddthinking I'll do my homework a bit. In my head one can consider two main types of air pollution: toxicity for humans and green house effect. I think for each type the question is can be answered (e.g.: for toxicity we must have the legal limits of concentration for each type of gas or for micro particles). Then I guess that indeed some ponderation for toxicity and green house effect in order to give a score. Maybe that would be a good first step? – user3371583 Jan 16 '15 at 16:12
  • I think there really needs to be some clarification: what exactly counts as 'old'? Go back far enough (or upscale enough) and you'd see wood, cloth, and leather used instead of plastic. Also, if the emissions from plastic were significant, wouldn't the plastic parts eventually evaporate completely? – jamesqf Jan 16 '15 at 19:08
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    I do hate dubious claims like this, there are different pollutants at play and we can't just do the sum of pollutant * pollutantbadness and compare. – Alec Teal Jan 17 '15 at 12:55

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