For this scenario, we assumed that our owner had bought a spacious 2005 Ford Five Hundred (now called Taurus), which got 21 mpg overall in our tests, and now wants better fuel economy while retaining a quiet, refined, comfortable driving experience. One option is a 2008 Toyota Camry with a four-cylinder engine. But according to our analysis, its decent 24 mpg doesn't make a big enough difference to offset the increased owner costs. Taking a much bigger step to the 34-mpg Toyota Camry Hybrid would seem promising, though its fuel economy benefits are tempered by the price premium that model commands. Even when considering a 44-mpg Toyota Prius hybrid, the numbers suggest that it would be prudent to hold on to the Five Hundred for another two years, then choose a more economical alternative. And by then, the redesigned, third-generation Prius should be on the market.




Large sedans

The appeal of the Chrysler 300C sedan has been its combination of style, interior space, and V8 power. But its 16-mpg fuel economy is now a true handicap. In an attempt to improve on that, we compared the 300C with the high-rated, V6-powered Honda Accord EX-L, another roomy sedan with a feature-rich interior, agile handling, quick acceleration, and 21 mpg. For even greater fuel economy, we also compared the 300C with the top-rated Nissan Altima, which has a frugal four-cylinder engine that gets 25 mpg. Here, the data shows the cost of switching from the 300C to the Altima 2.5 S is reasonable at today's fuel prices and more favorable at $5 a gallon. Over time, the slight upfront cost difference would favor the Altima. Either way, there will be cost benefits in the years to follow.