I assume you mean the current Beetle, not one of the old air-cooled ones. If so, ...

For 2006, there are only two engine choices: a 2.5-liter gasoline engine and a 1.9-liter diesel engine. The Convertible does not offer the diesel engine. Unless you really pile on the miles, the 2.5-liter engine probably is your best choice. Depending on where you live, diesel fuel may be hard to find and diesel engines don't handle short-hop (under 10 miles per trip) driving as well as gas engines can. On the other hand, the diesel will give you half-again the mileage on fuel that costs about the same as regular unleaded gasoline. And, at around-town speeds, it's as fast as the old 1.8 Turbo. Not noisy or stinky, either.

(BTW, I own a diesel VW Jetta and would not trade it [or my mileage] for anything.)

Previous Beetles offered a choice of three engines: a stock 2.0 liter, a turbocharged 1.8-liter, and a 1.9-liter diesel engine (again, no diesel on the Convertible). The 1.8 offers good performance, but requires premium gas. The 2.0 liter is often referred to as the "2.slow" but it is adequate. It could be more powerful, it could be quieter, it could get better mileage. But it gets the job done. The diesel I've commented on above.

Bear in mind that, if you want a diesel Beetle, most dealers will not give you any kind of break on the price. These cars sell as soon as the transport truck arrives and the dealers know it. With fuel getting expensive and staying that way, getting 35 mpg no matter how you drive (and up to 55 if you're careful on the highway) is mighty appealing.

Hope this helps....

thanks for the information.