Diesel cars are very popular in Europe where gasoline prices are very high. I understand VW may have one for the US market but I've never looked into it. I wonder how many of those small diesel cars could be legally imported into the US. There are many requirements for US cars that may not be compatible with those small diesels, such as 5 MPH bumpers, airbags, etc. At least we know the Prius meets US specs. Also, it'd be interesting to compare total emissions per mile for the Prius as compared to those diesels. We need to look beyond simple miles per gallon when comparing ecological impact of different types of cars.

The Prius is an interesting car from a technical point of view. I've ridden in a couple of them and they seemed good cars. Since almost all of the miles I put on my car is in town driving, I'll consider a hybrid when it's time to replace it. However, I'd only buy one if it makes economic sense. The current popularity of hybrid cars is driving up the price, even allowing for the tax credits. It'd make more sense to buy a economical car that gets 30 MPG (say, a Honda Civic) at $20,000 than a hybrid that gets 50 MPG if the price differential is too great, say $30,000. At $2 a gallon, a car that gets 30 MPG would use $667 per 10,000 miles compared to $400 for the hybrid. At $227 savings per 10,000 miles, it'd take 440,000 miles to recoup the higher purchase price. Even if gas prices soared to $4 a gallon would take 220,000 miles to recoup the higher purchase price, far longer than I'd ever keep the car.

I've heard insurance premiums are higher on hybrids, too, so that'd have to factor into the calculation.