Why diesels usually get better mileage

Fueleconomy.gov gives two reasons. First, diesel engines are more fuel-efficient and make more low-end torque than similar-sized gasoline engines. Second, diesel fuel contains roughly 10% to 15% more energy than gasoline. Together, that means a diesel vehicle can often go about 20% to 35% farther on a gallon of fuel than its gasoline counterpart.

Fueleconomy.gov also says today's diesels are much improved over diesels of the past. Better fuel injection and electronic engine controls have increased power, acceleration and efficiency; new engine designs and noise- and vibration-damping technology have made them quieter and smoother; and cold-weather starting has improved.

From Diesel Vehicles (fueleconomy.gov), read November 9, 2026.

Diesel vs. gas: an EPA pickup comparison

To see the trade-off in real numbers, here are the EPA ratings fueleconomy.gov lists for three engines in the same 2026 Chevrolet Silverado 2WD pickup. The annual fuel cost is fueleconomy.gov's estimate based on 15,000 miles a year, 55% city driving and the current fuel prices when we checked on November 9, 2026:

From the 2026 Chevrolet Silverado 2WD side-by-side comparison, EPA records 49361, 49362 and 49358 (fueleconomy.gov), read November 9, 2026. Fuel cost estimates change with fuel prices; your mileage will vary.

In this example the diesel has the best mpg by a wide margin, yet its estimated annual fuel cost on November 9, 2026 was slightly higher than the V8's and higher than the turbo four's, because diesel fuel and gasoline are priced differently. If you tow or haul often, the diesel's low-end torque may matter more to you than fuel cost; if you mostly commute, run the numbers first. Fueleconomy.gov's side-by-side tool lets you compare vehicles' EPA ratings and fuel costs.

Which diesel fuel should you use?

Fueleconomy.gov says owners of 2007 and newer diesel vehicles should fuel them only with ultra-low sulfur diesel (ULSD). ULSD contains 97% less sulfur than low-sulfur diesel (LSD) and allows improved pollution control devices that sulfur can damage. It is also safe to use in older diesels. As of December 1, 2010, all diesel fuel sold in the U.S. must be ULSD, and pumps dispensing it must be labeled (except in California).

Some pumps sell biodiesel blends. The Alternative Fuels Data Center (AFDC) says biodiesel is made from vegetable oils, animal fats or recycled restaurant grease and is used in diesel (compression-ignition) engines. Its cold-weather performance depends on the blend; in general, smaller biodiesel percentages do better in the cold, and No. 2 diesel and B5 (up to 5% biodiesel) perform about the same. In winter, fuel suppliers add cold-flow improvers. Check your owner's manual for the blends your engine is approved to use.

From Ultra-Low Sulfur Diesel (fueleconomy.gov) and Biodiesel Fuel Basics (Alternative Fuels Data Center), read November 9, 2026.

Are diesels clean?

Fueleconomy.gov says today's diesels must meet the same emissions standards as gasoline vehicles, made possible by advances in engine technology, ultra-low sulfur diesel fuel and improved exhaust treatment. It adds that emissions of particulates and smog-forming nitrogen oxides (NOx) are still relatively high, and that cleaner fuels and emission-control advances will reduce them.

For other drivetrain questions, see our guides to CVT transmissions and auto start-stop.

From Diesel Vehicles (fueleconomy.gov), read November 9, 2026.

Service at Elgin Auto Sales & Service Center

Have a vehicle that needs attention? Schedule service or see our service specials.

Our service department at 1200 E. Chicago St. in Elgin is open Monday to Friday 8 a.m. to 5 p.m. and Saturday 8 a.m. to 4 p.m., and is closed Sunday. Get directions.