Dear Car Talk:

I want a VW Tiguan, but VW does not offer one with the TDI diesel engine in the U.S.; it offers other cars with that engine, like the Jetta and the Beetle. If I bought a gasoline-powered Tiguan, what would it take to swap a TDI diesel engine into it?

-- Robert

About $15,000-$20,000. Maybe a little less if you're willing to marry a VW mechanic.

The diesel engine itself probably is a $10,000 part. But there are all kinds of modifications you'd probably need. The exhaust system would be different, and would require a scrubbing system. The emissions system would be different. The computer would be different. The transmission may even be different. I think you probably can keep the rear-view mirror and the cup holders.

It might be easier to buy a TDI Jetta and then put a Tiguan BODY on top of it, Robert! Or get transferred to Europe for a few years and drive one there and get it out of your system.

It's an enormous and pretty much pointless endeavor, Robert. It would take you half a century to recoup the costs in the form of the extra mileage you'd get with a diesel. And by then you'll be wanting one of the new, 2065 water-powered Tiguans anyway.