Online auto research site launched its Fuel Economy Guide this week. This new service provides tips for improving gas mileage, information about current hybrid cars and diesels, as well as alternate fuels we can expect to see in the future, advice on shopping for fuel efficient cars, lists of the top 10 most fuel efficient cars, trucks and SUVs, and the latest relevant news. In addition, the Fuel Economy Guide features an article explaining why the EPA's fuel economy estimates printed on window stickers are not necessarily close to the mileage that consumers will get when actually driving the car or truck.