On
www.fueleconomy.org for the 2006 Jetta TDi automatic the combined EPA estimate is 33 MPG. Drivers report 40.8 MPG.
If you apply a 'correction' to the 2009 Jetta with the automatic based on the disparity , the figures go from 29/40 city/hwy to 36/49 city/hwy. The combinde number for the '09 is also 33 MPG, so drivers may actually achieve around 40 MPG.
Very assumptive, I know, but just food for thought, especially if you compare these very theoretical numbers with a 2008 Jetta 2.5 with 21/29 MPG estimates (chosen since 2009's don't have any driver reported figures yet). Combined estimate is 24 MPG, and this is the average of the reported figures.
40 MPG is
67% higher than 24 MPG. (40/24)*100 (%)
You would spend 40% less on fuel. ((40-24)/40)*100 (%)
Currently diesel is roughly 18-25% more expensive, so you still have a net savings.
I drive about 13,000 miles a year now. I see gas around $4.20/gal & diesel around $5.25/gal where I am. getting a 40 MPG diesel sedan over its 24 MPG gas counterpart would save me personally $570 per year. From a purely economic standpoint this would need to be weighed against the diesel's higher inital price. Of course, this doesn't take into account my opinion of diesels--I think they're cool, and would be willing to get one (provided I like the underlying car) even if the cost issue was a wash.