40x sounds like a big number, but what is the extent of that number? How does it factor into real world situations? Also, what is the trade off? Don't diesels emit less Co2 than gas cars, but higher NOx? Does the significantly better fuel efficiency (and everything that entails, from processing, to transport, to consumption) offset the higher NOx? Is 40x higher still cleaner than 10, 15, 20 years ago?

What is the BIG picture here? Everyone is just saying "omg NOx".

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03 3.0i mt
89 325is