I had an older model VW TDi. At the time, the only diesels you could get in the US were VWs and Mercedes. I asked a mechanic at the dealership why, and he told me a lot of diesels won't meet US standards for cleanliness, so they stay in Europe and Asia.
I wonder if VW gamed them to keep importing diesel vehicles - we diesel heads are a small, but cultish bunch of people. 45 mpg was pretty much my avg no running the AC, around 40 with the AC on. Just in case you were wondering.
And since people are misinformed, the increase in milage is more than offset by the price of the fuel. When I first got mine, diesel was cheaper than regular gas and it was a huge money saver, but once low-sulphur was mandated, diesel became more expensive than premium gas and it was a money loser.