A new report from Kelley Blue Book (KBB), the used car pricing guide, is showing rising values for fuel-efficient models, as more Americans look for vehicles that will help them save some money at the pump.

The KBB Market Report for May 2011 indicates that these cars are in high demand and are driving up used car prices very quickly. As compared to January of this year, prices on average are up 20 percent across the fuel-efficient market segment. And with gas prices remaining high, KBB doesn't predict that these prices will be dropping off anytime soon.

For example, the report shows that drivers looking to buy a used Toyota Prius will be paying $3,800 more than they would have in January, due to a combination of both the gas crisis and an expected short supply of the vehicles because of the Japanese earthquake. The Ford Fusion saw a similar price jump at $1,800 over its January value.

Of course, the pendulum swings both ways, and dealers are also paying a lot more for fuel-efficient vehicles. If you've been thinking about trading your Prius or another fuel-efficient car, there's no better time to do so, as you could end up getting a great deal.