The Audi Q7 is one of few SUVs in the United States with an available diesel engine.

Clean diesel automobile sales in the United States increased 35 percent in the first quarter of 2012 compared with the same time one year ago, marking a consistent increase in diesel car sales, according to a study by and Baum and Associates.

In a press release, Diesel Technology Forum, a non-profit organization, says clean diesel vehicle sales increased by 21.2 percent in January 2012. February diesel vehicle sales were up 42.9 percent, and in March, sales increased by 39.6 percent.

With gas prices expected to peak at about $4 per gallon this summer, the popularity of diesel cars is understandable. Diesel engines are about 30 to 35 percent more fuel-efficient than a similar-sized gasoline engine, according to the Environmental Protection Agency, and have more torque, which makes them feel more powerful and faster.

Though the diesel auto sales increase is significant, The Detroit News notes that diesels “still account for less than 1 percent of all vehicles.”

There are few diesel vehicles currently available in the United States, and more will hit the market in the near future. The Porsche Cayenne, Audi A6, Audi A8, Audi Q5, Jeep Grand Cherokee, Cadillac ATS and Chevrolet Cruze are all expected to offer diesel engines, The Detroit News reports.

Excluding heavy-duty trucks with diesel engines, these models will join the batch of diesel cars and SUVs available now. These include the Volkswagen Jetta TDI, Volkswagen Golf TDI, Volkswagen Passat TDI, Volkswagen Touareg TDI, Volkswagen Jetta SportWagen TDI, Audi A3 TDI, Audi Q7 TDI, Mercedes-Benz ML350 BlueTEC, Mercedes-Benz GL350 BlueTEC, Mercedes-Benz R350 BlueTEC, Mercedes-Benz S350 BlueTEC, Mercedes-Benz E350 BlueTEC and BMW X5 xDrive35d.

If you plan to buy a diesel vehicle soon, here are some of the deals on these models in April:

2012 Volkswagen Jetta TDI: 0.9% for 60 months

2012 Volkswagen Jetta SportWagen TDI: 1.9% for 60 months

2012 BMW X5 xDrive35d: $599 a month for 36 months with $3,824 due at signing, or 1.9% for 36 months

Shopping for a new car? Check out the U.S. News rankings of this year's best cars and check out the latest car deals. You can also skip negotiating with a dealer by using our Best Price Program. Also, be sure to follow us on Twitter and Facebook.