You can opt for a clean-diesel engine in the Volkswagen Jetta SportWagen. But do your diesel-powered savings plans actually add up?

(Courtesy of Volkswagen of America. Inc.)

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Nothing makes you feel more broke than a trip to the gas station. You have to stand there watching the numbers flick by, going up and up and up. You start daydreaming of those clean diesel cars, the ones that get around 40 miles per gallon (17 kilometers per liter). Sure, they cost a little more, but in your daydream, you'd make up the difference with the savings on fuel. Good idea, right? Well let's find out if your daydreams have any truth in them.

As an example, let's have a look at the 2014 VW Jetta SportWagen since it comes in both gasoline and clean diesel versions that are nearly identical -- except for the engine, of course. The basic gas model sells for $20,795, and the diesel is listed at $26,250, a difference of $5,455. But can going a little farther on a tank of gas really make up more than five-thousand bucks? According to EPA estimates, the gas model gets 26 miles per gallon (11.1 kilometers per liter) combined city and highway and at 2013 gas prices, you'd pay around $2,100 a year for fuel. The diesel gets 34 miles per gallon (14.5 kilometers per liter) combined, but you have to remember that diesel fuel is a bit more expensive, too. In the end, the EPA estimates you'll pay about $1,750 per year in fuel. That's $350 less. High five!

But hold that high five for just another minute, kids. With $350 in fuel savings per year, it would take 15.6 years to make up that $5,455 difference.

Now let's say that you're already driving an SUV with rotten mileage. Maybe it's something like a 2014 Chevy Suburban with four-wheel drive. That monster gets 17 miles per gallon (7.2 kilometers per liter) combined, and the EPA estimates tell us that you're likely spending about $3,200 a year on fuel. Yikes. Switching to a gas-powered Jetta SportWagen will certainly help, but if you opt for the diesel-powered SportWagen, you'll save $1,450 a year. Now we're talking!