) -- Two ways for automakers to get to higher fuel efficiency ratings: develop new vehicles or redesign old ones.
New vehicles such as the
Cruze have done well for the Detroit Three, and new models such as the Volt point the way to the future, but redesigns to existing vehicles can be quicker and less costly.
"It's far more cost-effective to work with what you have and to provide consumers with options that are more to their liking," says Ivan Drury, an analyst for Edmunds.com, which has compiled a list of the 10 vehicles with the biggest mileage gains since 2008.
In general, vehicles made it to the list because at some point between 2008 and 2012 they began to offer options such as six cylinders instead of eight, or four cylinders instead of six, or diesel engines. The move to four-cylinder engines has probably been the most important step as the overall U.S. fleet has become more fuel efficient.
One result of the change is that U.S. automakers are better prepared for high fuel prices. In February, the industry enjoyed dramatic sales growth despite a rapid increase in fuel prices.
(GM - Get Report)
sales conference call last week, executive Don Johnson was asked whether the automaker would be in as good shape if it had the same model lineup today as it did in 2008, a year industry sales began a two-year decline that took them from 16.1 million in 2007 to 10.3 million in 2009.
"We wouldn't be," Johnson responded. "We're in a very good position now because of our car portfolio complementing our strong trucks."
Among the top 10 cars in terms of improved fuel efficiency by percentage since 2008, GM has two, the Buick LaCrosse and the Chevrolet Equinox.
Here is the list, compiled by Edmunds.com: