High sticker prices and long waiting lists for popular fuel-efficient vehicles like the Toyota Prius have some consumers looking for cheaper alternatives to save money at the pump.

Economy cars that were built in the mid- to late 1990s have seen a dramatic increase in the number of consumer searches on Cars.com.

Cars like the Geo Metro and the Geo Prizm have seen consumer searches rise by more than 200 percent year over year. Renewed interest in these cheap, fuel-efficient vehicles has also driven up their prices: Several Geo Metros from the mid-'90s, which have a book value of about $1,300, are listed for sale on Cars.com for more than $4,000.

"Despite their renewed popularity and the ability to potentially save some money, there are several precautions that people should take when looking at older subcompacts like the Ford Festiva and Geo Metro," said Cars.com senior editor Joe Wiesenfelder. "While they may save money on gas, many of these cars can bear greater costs when it comes to safety and reliability, which is part of the reason these cars weren't popular when they were first introduced. Over time automakers have both changed the way they construct vehicles and added safety features not found in earlier models, improving crashworthiness across the board."

Wiesenfelder recommended several tips to look at if shoppers are considering older, fuel-efficient vehicles:

Consider a newer used car, even if its fuel economy isn't quite as good as an older one's. The earlier subcompact cars' strength -- good gas mileage -- comes from small size, light weight and simplicity, all of which are weaknesses in terms of crashworthiness. Comparable small cars from the past several years are designed to be safer, and the field as a whole is more reliable than it was 10 years ago.

Ensure that the car has side-impact airbags: Though they proliferated in small cars in the early 2000s, side-impact airbags were almost always optional, so availability is limited. Cars equipped with them will have an "SRS" or "airbag" label on the side of either front seat's backrest, facing the door, and/or a similar label on the pillar next to the windshield or between the side windows, indicating a curtain-style airbag. Side airbags don't ensure high crash-test results, but their effect is overwhelmingly positive.

Do the math and consider keeping your current car. The prospect of infrequent fill-ups and less money spent on gas is attractive, but it doesn't make replacing a car that's already paid for a better move in the long run. Four or five mpg looks like a big improvement, but it depends on how efficient your current car is. Calculate how much money you're likely to save with a more efficient car versus the cost and possible sacrifice of giving up your current ride and buying a different one. Demand is high for efficient cars and low for guzzlers, so you might see a significant loss before you realize a gain -- if you do at all.