If you have a long highway commute and you're considering a hybrid to help you cut your gas expenses, a new report says you should think again.  Popular Mechanics tested a Toyota Prius against Volkswagen's New diesel-powered Jetta TDI, and the results were a little surprising.

The Prius easily beat out the Jetta in congested city driving.  But on the highway, the diesel topped the hybrid.

PM explains, "Our highway test loop took us from the cool ocean breezes of Santa Monica to the hot desert winds near Palm Springs. We set the cruise control to 65 mph as often as possible to maximize fuel economy."  At the end of the route, the gauges showed that the Prius had gone the distance using 44.8 miles per gallon.  The Jetta? 45.4.

Jetta drivers had a lot more fun on the route as well.  "When we absolutely needed to punch the throttle to merge with traffic, the Jetta left the Prius behind. Shift the DSG into Sport mode, and it will downshift rather brilliantly as you enter a sweeping bend. The Jetta's drivetrain almost encourages you to burn fuel-that is, it's actually fun to drive. And the same cannot be said for the Prius."  Diesel fuel is slightly more expensive than gasoline, but its base price comes in slightly lower than that of the Prius, and it's eligible for a $1,300 federal Advanced Lean Burn Technology Motor Vehicle tax credit.  "Surprisingly enough, the Prius is not eligible for this tax credit."

Autoblog Green is a little skeptical, noting that, "In the city, which is the traditional edge for the all hybrids, the Prius earned its fuel mileage crown back by besting the TDI by over ten miles per gallon."

Newsday notes a few other factors to consider.  "Of course, you have to factor in driving demands. The numbers look better for the Jetta if you're a long-distance, Willy Loman type. The Jetta and the Prius have almost identical base MSRPs, but California dealers are still sticking Prius buyers with huge premiums. Not to be outdone, VW dealers have started tacking premiums onto the Jetta TDI. How do you account for that in your cerebrations? What about the fact that, all else being equal, diesel powertrains offer more longevity and require less maintenance? Ay. My head hurts."

We'll add this: at the moment, it's still possible to find a Jetta TDI.  Priuses, however, have been flying off of dealer lots so fast that it's difficult to buy one if you are in the market. 

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