jetta-fighting diesel?

I'm really curious as to why the north american automakers are so willing to hand over sales of small cars with fuel-sipping diesels? I
live 100 km from my workplace, and when I compare the likely 500 km I'll get to a tank of gas on a Cobalt I'm considering, to the Jetta TDI wagon my boss has (he arbitrarily fills the tank at around 900 km, whether it's low or not), the Jetta looks like a real all-star - except that I'm not particularly attracted to German cars. I'm sure the ecotec is a great little engine, but for those of us who do a lot of commuting, is there any chance of getting an engine that will REALLY make a difference at the pumps?
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