colder air should get you better mpg, lower temp equals more dense equals more oxygen. The weather was about the same on my trip.
45mpg would be nice, but my truck weighs about as much as three jettas You could park your jetta in the back of the truck, and I would still get 23mpg Did I mention it has 570ftlbs of torque?
Too bad they don't put diesels in more stuff over here, can you imagine how much farther you could go in a regular passenger vehicle that doesn't need all that power?