CAMBRIDGE, Mass. — CarGurus, an auto research and shopping site, expects prices on fuel-efficient, used vehicles to increase 15 percent by August as gas prices continue to approach $4.50 a gallon.

CarGurus analysts say the correlation between gas prices and prices of fuel-efficient, used cars has been notably high over the past 13 months. As gas prices climbed to nearly $4 a gallon last year, demand for used fuel-efficient cars followed, which sent prices on such vehicles up soon after.

This year, CarGurus analysts expect to see a similar price correlation, according to the company. The main difference is that prices on fuel-efficient used cars never fully recovered from last year's highs, so consumers will see prices peak in August at a level that’s 10 percent higher than the same time last year.

"Gas prices have proven a reliable indicator of where used-car prices are headed, and consumers in the market for a fuel-efficient, used car this year should be mindful of that correlation," said Langley Steinert, founder and CEO of CarGurus. "The best advice for shoppers is to get ahead of the cycle by buying soon, when they will find the best deals on small, fuel-efficient used cars. Alternatively, consumers should consider waiting until the fall and winter months when there is typically less price volatility in the used car marketplace."

For more information, visit www.cargurus.com/Cars/price-trends/.