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Comment by benjarrell | Hacker News Reader

Diesels are required to have a particulate filter: https://en.wikipedia.org/wiki/Diesel_particulate_filter

Which is usually used with exhaust fluid: https://en.wikipedia.org/wiki/Diesel_exhaust_fluid

DEF (AdBlue) can significantly reduce NOx emissions. It's now standard in modern heavy diesel trucks, busses, etc. However, it's very rare to find it in light diesels such as cars and SUVs which often have real-world NOx emissions far in excess of what emissions standards allow.

DPFs remove visible soot from diesel emissions, but their actual benefit for health is less clear. They don't trap the ultra-fine, PM2.5 invisible sooty particles which are the most dangerous because they can penetrate the lungs and enter the bloodstream. These particles are associated with increased risk of cardiovascular diseases and cancer.

DPFs also tend to break down after a few years of use. Often, they end up being (illegally) removed by owners who don't want to pay for an expensive replacement.

DEF isn't that rare in passenger vehicles anymore. Ford's new line of diesels tend to use it, BMW and Mercedes use it, and I feel a couple of other 'new' small diesels are using it as well. It used to be rare, but I think enough people realized they can't meet standards without it and now they are all moving towards it.

Correct me if I'm wrong, but most regular consumer vehicles aren't required to have a urea/DEF system, but all the big trucks and commercial vehicles tend to.

Somebody was blaming this on trucks, but I'm thinking this might be the opposite - their small cars as it was with VW because they don't have these sorts of systems in place.

You're right. It's now light diesel vehicles that are the primary problem with regard to excessive NOx emissions. At least in Europe, where there are a huge number of light diesel vehicles on the roads.

But there are, of course, a lot of old pre-DEF heavy vehicles on the roads too that would not comply with modern emissions standards.

The engine in question did have a DEF system though...

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