A study by the Union of Concerned Scientists is claiming that increasing fuel economy of the US vehicle fleet to 35mpg by 2018 would have huge economic benefits for the United States. The study claims that consumers will save $61 billion on fuel expenses and 241,000 new jobs will be created. The job gains come from the assumption that the money saved will be spent on new, more efficient vehicles and on other goods and services.
The study was based on a model that includes data from a number of different industries. Industrial states like Michigan, California, Texas and others that use the most energy would have the most to gain from the savings. The savings are based on a gas price assumption of $2.55 a gallon. It's not entirely clear from the report how the price of gas is adjusted over time to come up with the savings numbers. Undoubtedly, raising fuel economy would be beneficial but how much money would be saved is highly dependent on where the price of fuels used in the latter half of the next decade go.
[Source: Union of Concerned Scientists]