[grandalf]

That is a good point. You may very well be correct.

I think that from an economic perspective, reduced fuel economy is also beneficial to the environment because the driver is less likely to spend money traveling (keeping the vehicle's engine running, producing pollution) when the cost is higher.

However if the vehicles in question were part of a fleet whose behavior would not change much based on fuel costs, there would seem to be nothing but downside to diminished fuel economy.

What's interesting to me about this is that it seems that a few other manufacturers were able to engineer diesel engines with power, fuel economy, and emissions characteristics that met the guidelines without cheating. It would seem that this is quite a feat, if VW had to resort to gaming the system.

On a tangential note, I also find it interesting that we accept certain tradeoffs about noise pollution vs air pollution, since if we simply removed mufflers from cars, fuel economy would increase.

[sokoloff]

It is unlikely that a reduction in fuel economy of X% would incent a reduction in driven miles of more than X%. Fuel cost is a minority component of total lifetime cost of the vehicle.

Most people have a (perceived) fixed distance of driving they need to drive. A 10% reduction in mileage won't have drivers biking 1 day every other week.