This article from the 2006 Wards Auto Ten Best Engines List describes the best way to achieve the EPA mileage estimates for hybrids.First among our complaints, pointed out by a growing number of journalists and disgruntled owners, is real-world fuel economy far less than what is advertised.Second, fuel economy is affected too much by driving style and ambient temperature.The Lexus RX 400h is the epitome of luxury and environmental friendliness when we moved silently through stop-and-go traffic on full electric power. But once the vehicle's internal combustion engine gets involved with propulsion, we were less impressed. During hard acceleration it doesn't have the premium sound we expect from a vehicle with a base price approaching $50,000. Plus, we were underwhelmed with our 25 mpg (9L/100 km) average.NASA astronaut Ken Mattingly spent tedious hours in a flight simulator figuring out a start-up sequence that used only 20 amps for an energy-starved Apollo 13. That made for compelling drama in a movie.Employing the same power-saving tactics just to squeeze out something close to the EPA mileage from a Civic Hybrid on a cold day is a bit less engaging.Want something close to its alleged 49/51 mpg (5L/100 km/4.6L/100 km) on a frosty morning? Forget about warming up the engine or using the defroster. Scrape the windows by hand, stay off the throttle and the expressway and get ready to shiver.Enduring that kind of inconvenience is fine if you need to get back from space with your fuel cells spent, but not when you're just heading to work.http://wardsautoworld.com/ar/auto_best_engines_10/index.html