The test could even be met without the urea system. But the car would have to run rich and flush out its NOx system more often, which uses fuel and lowers performance. The thing that was so marvelous about the Volkswagen TDI engine was how all of its performance numbers and fuel economy were better than what was advertised. Other manufacturers were racking their brains trying to figure out how they did it.

It seems a little hard to believe that other manufacturers had no idea how they did it. If it was so confounding it could quickly resolved by plugging in an analyzer and run a test cycle...

Maybe VW isn't the origin of this, they could have seen another manufacturer doing something similar, decided to join in and took it too far.

They may have done exactly that, but not in highway conditions, and so got fooled just like the inspection locations.

What's the point? Urea is almost free. I don't get why it was ever a big deal.

The DEF itself is pretty inexpensive (though not free, like $8/gal), but the system to keep it from freezing in wintertime is actually kind of a pain, since it freezes at -10C but decomposes around 60C so your heating element can't be too hot. The cost savings from not using it were rather substantial. Volkswagen TDIs were the cheapest performance diesel cars by a rather large margin.

It's an active expense that doesn't directly benefit the user, and disables your otherwise mechanically sound vehicle when it runs out; both of which tend to rub people the wrong way. Also I think there was something about german companies colluding over adblue tank size to force more refills, but don't quote me on that.

Also it's a user-maintenance thing. One more thing to refill on top of your windshield wiper fluid.

I forget if it was VW or Mercedes, but one of them branded theirs as "blue-tec" or something that doesn't sound like you're handling piss bottles. Let the mechanic worry about that.

In all fairness, the urea systems are really annoying. I was driving a rental vehicle and I got a warning that it was out of urea in the middle of nowhere. I stopped at a gas station which did not have any and the vehicle would not start until you put urea into it which I could not find in the middle of the desert.

I had a co-worker who had a similar horror story. Drove out into the Alaska outback in a modern truck (<3 years old), there was some issue with the emissions reduction system (DEF heater failed), the vehicle went into "limp" mode after 50 miles (40 MpH speed limited) and displayed a warning it would limit them to 20 MpH after another 50 miles.

There literally wasn't any dealer or provider that could do anything before it hit 20 MpH limit, and the truck wound up being flatbed-ed (luckily the manufacturer picked up the bill, but still).

This definitely makes diesel vehicles less reliable, more expensive to maintain, and likely reduces their lifespan. If I purchased a truck I'd go gas.

I imagine that this is when I would perform a hard reset (by disconnecting the battery or pulling the fuse) of the ECU.

Not sure if it would work on that vehicle, but it generally clears emissions codes and the like, even on fairly recent vehicles. Its possible it might have let the car drive another 50 miles or so.