Gasoline prices continue to climb, steadily approaching record highs well in advance of summer. As consumers look to ease their pain at the pump, the difference between the most and least fuel-efficient cars is coming into sharp focus. We ran the numbers and, depending on which model you choose, found that the annual fuel cost difference can be staggering.

In fact, the difference is so dramatic that for those drivers who can trade an older gas-guzzler for a smaller, thrifty vehicle will see savings of $2,000 year, or more, in operating costs. Of course, not everyone can make such a bold move, as some large vehicles were likely bought for a purpose, such as transporting the family or hauling a boat. In this economy, while the family continues to live under one roof, the boat may well have sailed on to another harbor, allowing for some transportation right-sizing, if not true down sizing. Translation: If you can live without a big, trailer-towing truck, consider dumping it for something more fuel efficient.

Whatever your situation and car-buying budget, there are an increasing number of fuel-efficient choices on the market now, as the automakers race to meet consumer demand and increasingly stringent fuel economy standards.

As the chart below indicates, the extreme in fuel savings is well over $2,000 a year though for many people, saving $1,000 to $1,500 is quite feasible. For high-mileage drivers logging 15,000 miles a year, the savings correspondingly increase, with the extreme downsizing resulting in saving $3,000 a year in fuel costs--without turning to a pure-electric car.

The calculations are based on the national fuel prices from the Energy Information Administration, assuming 12,000 miles annually and using Consumer Reports test results for energy consumption rate. The vehicles in this list use a variety of fuels, including diesel and premium. The prices are based on the fuel recommended by the manufacturer.

For the Nissan Leaf, we calculated the miles-per-gallon equivalent based on our measure of the small hatchback consuming electricity at 3.16 miles per kilowatt hour (kWh) and a 3.5-cent running cost based on the national average of 11 cents/kWh. The Chevrolet Volt required a bit more math, combining the electricity and gasoline consumption. Our composite rating for the Volt is 61 MPGe (with 99 MPGe on electric and 32 mpg on gasoline only). For these calculations, we assumed 70-percent of driving would be done on electricity, 30 percent on premium gasoline.

The list highlights the extremes, though there are smart choices in every price category and car type. Explore our ratings to see what fuel economy vehicles deliver in our tests. Pricing, owner cost, reliability, and other information is available through our New Car Selector and on the individual model pages.

Learn how to get the most mpg now, with your current car.

See our guide to fuel economy special section for more tips.