Researchers at MIT have released a new report showing that increasing fuel efficiency standards in order to reduce greenhouse gas emissions costs our economy six to fourteen times more than would increasing the gasoline tax. Increasing fuel efficiency standards for new cars, they point out, does nothing to reduce emissions from the existing fleet of older vehicles on the road. A higher fuel tax, by comparison, would encourage all drivers to use less fuel by driving less and aiming for the best mileage possible. A higher gas tax is a tough sell politically because the price hike is highly visible to consumers. In contrast, consumers probably won’t notice the higher cost they pay for a more fuel efficient car – especially because the portion of vehicle cost attributable to efficiency technologies will be impossible to calculate.