Want to save money, conserve energy and do what's best for the environment at the same time? The next time you're in the market for a new car or truck, go diesel.

Vehicles powered by diesel engines are the most fuel-efficient on the market today. They burn 30 percent less fuel than their unleaded-gas counterparts, meaning they get more miles to the gallon. They also are more powerful. Since they produce higher torque at low engine speeds, drivers have an easier time merging into traffic, accelerating onto the highway, passing slow-moving vehicles, pulling trailers and climbing hills. Diesel engines are also more environmentally friendly, as they produce 25 percent less carbon-dioxide emissions.

The strongest demand for diesel engines is in Europe, where they account for about 42 percent of the passenger-vehicle market. But with the price of unleaded gasoline at or near all-time highs in the United States, there is growing awareness here of the advantages diesel offers. Jeep, Mercedes-Benz, Volkswagen, Chevrolet, Dodge, Ford, GMC and Hummer offer diesel models of their most popular U.S. cars, trucks and SUVs.

But switching to diesel isn't the only way you can save money on fuel.

"It's also a good idea to look for ways to enhance the efficiency of your diesel engine," said Tom Wicks, manager of product development for Gold Eagle, an industry pioneer in the production and distribution of aftermarket fluids and additives.

Here are his recommendations for diesel owners on how to maintain their engines:

• Change and clean the air filter regularly. Diesel engines take in a lot of air for combustion, which powers the engine. A plugged or dirty air filter can choke off the airflow to the cylinders, reducing fuel economy and available power.
• Clean and lubricate the engine's fuel injectors and remove deposits caused by dirt, sand and fuel impurities by adding DieselPower fuel-system treatment to your tank. Clean injectors mean better combustion, which translates to more power, better fuel-efficiency and a longer engine life.
• Change the oil and oil filter at recommended intervals. Oil is part of the friction-reducing, lubricating lifeblood of the engine, and because it can pick up dirt that makes it past the air filter, it needs to be changed often. If it isn't, the dirty oil will cause engine wear and reduced fuel economy over time.
• Maintain the recommended tire pressure for the load being carried. Low tire inflation means high rolling resistance and reduced fuel economy.