When booking a rental car for continental Europe, ask for a diesel vehicle for both economy and comfort. European clean-diesel technology produces quiet, low-emissions vehicles that achieve better mileage than their gasoline-powered peers. Diesel is also cheaper than gasoline. In Spain, I drive a Seat Altea, a mini-SUV. It’s a little more expensive per day than the cheapest econobox, but pays for itself in fuel economy while providing more leg- and luggage room. In combined city and country driving, I get about 42 miles per gallon (17-18 kilometers per liter). For average European fuel prices, see www.drive-alive.co.uk/fuel_prices_europe.html.