The autos section at business magazine Forbes has compiled a top ten list of most fuel efficient luxury cars. While some of the vehicles on the list seem obvious - the Mercedes-Benz E320 BlueTec diesel and the hybrid Lexus GS450h - there were some surprises. Giving Porsche's complaints about European Union plans to impose limits on carbon dioxide emissions, finding the Boxster sports car on the list might come as a shock. However, driven tamely, it can achieve pretty decent mileage. Of course like many sports cars, it thrives on being driven quickly and doing so can easily drive the mileage into the single digits. On the other end of the spectrum most might not consider the Volvo C30 a luxury car. The little hatchback is based on the same platform as the European Ford Focus and, although well appointed, calling this a luxury car might be a stretch. Also, the 19/27mpg rating for such a small car is hardly exceptional and barely matches the 19/28 of the Porsche.