I'm considering on buying an older car but I haven't decided if it should be gasoline or diesel powered.
I would like to choose a diesel, but I'm considering the negatives:
Is there something I personally can do to emit less NOx, smoke, smell and dust?
By crushing the car and recycling the metal. That's how.
Diesel cars are awful and there's pretty much nothing anyone can do about it, if the recent VW diesel cheating scandal hasn't already made that abundantly clear. Volkswagen had done everything they could, using the latest technology, to reduce the emissions of these cars, but they still couldn't get the emissions down to acceptable levels. So they cheated and made the cars run super lean when the GPS told the car that it was at a testing facility. Doing this on the street would make real-world owners complain about a lack of power though, and they couldn't have that.
Now what they're doing is replacing their diesel models with electric drive trains. They're literally giving up on diesels for consumer applications.
If you'd like to do this (for a myriad of reasons, including leaving the awfulness of diesel engines behind, and cutting the cost of fuel to next to nothing, nevermind a super reliable, quiet ride that requires nearly no maintenance), then you can buy an older Nissan Leaf or Renault Zoe for a fraction of their original sticker price. If you have 220v mains in your house (which describes pretty much the whole of the UK and Europe), then you don't even need to do anything extra. The car comes with a charger that will fill it within a few hours while you sleep, and there are now lots of fast chargers throughout the countryside.
It largely depends on the sort of driving you do - if you do lost of short journeys, buy petrol (or electric), if you mostly do long journeys, buy Diesel.
The best thing you can do to reduce the impact is simply to drive it less - The fewer miles you do, the less emissions you create, so consider using the train instead wherever possible, and walk/cycle for shorter journeys - this latter point is most important, as Diesel cars are very inefficient when cold, and so are very bad for short journeys.
Make sure the car is well maintained, particularly any emission controls such as Diesel particulate filters and echaust gas recirculation systems.
Keep the tyres in good condition and correctly inflated - a significant proportion of the particulate emissions from a car comes from tyre, road and brake wear - this Defra Report (pages 84-85) suggests that in 2009, 12.4ktonnes of PM2.5 emissions came from vehicle exhausts, and 7.8ktonnes from non-exhaust vehicle emissions - but by 2020, the exhaust emissions are predicted to fall to just 2ktonnes, while the non-exhaust emissions would increase to 8.8.
Older Diesel cars will run on vegetable oil, which doesn't really help with the point-of-use emissions, but does reduce the overall impact, as you're not using as much unsustainable fossil fuel. Similarly keeping the car going for as long as possible - it may not directly reduce the particulates in the immediate vicinity, but it's better for the overall environment than scrapping it and creating a new vehicle. This Telegraph Article, quoting from Mike Berners-Lee's book "How Bad Are Bananas? The Carbon Footprint of Nearly Everything", calculates the CO2 emissions from a new Golf to be 22t for manufacturing + 40,000 miles (the average in the UK for 5 year's worth of driving), compared with 11t for buying a 10-year-old one and driving it for another 40,000 miles - and if you make the concious effort to reduce your milage, the old one would be 5.5t for 20k miles, whereas the new one would be 19.9t - an even bigger difference.
There may be a solution (although not cheap) from these people in the UK http://www.cgon.co.uk/
Responding to Dee's comments below: What you could do is buy the ezero1 unit that CGON (who are based in the UK) manufacture for around £700. It claims to reduce emissions and increase efficiency. However, the installation service only seems to operate in the UK at present. The page relating to independent (but apparently paid for, so arguably not independent) testing is here: http://www.cgon.co.uk/emissionresults
You may buy a simple petrol car and have LPG (propane) conversion, which is cheaper to drive and more eco-friendly (before the expensive hybrids or pure electric options). Though, it depends on the availability of LPG dispensers in your region
