What do prices at the pump have to do with prices at the used car lot? They actually tend to mimic each other. Higher gas prices tend to cause drivers to want to spend less out of pocket on their automobiles. That means rising demand, as well as rising prices, for used cars—fuel-efficient used cars especially. Used car prices spiked last summer as gas prices soared, and then spiked again earlier this year as the national average neared $4 a gallon. Now that gas prices are retreating, relief is also in sight for consumers in the market for used cars.