ALTOONA, Pa.—Sheetz is extending its discount on diesel exhaust fluid (DEF), reports The Trucker. Last month, Sheetz lowered the price of its DEF to 99 cents a gallon through the end of January at select locations. The discount will continue through February 28.

The average price of DEF at Sheetz’s stores was $3.50 a gallon before this offer.

“This reduction has resulted in a savings of approximately $15-$75 for customers depending on the size of their DEF tank in their vehicle. This offer only applies to bulk DEF sold at Sheetz’s truck diesel dispensers,” according to the company.

DEF is used in vehicles with diesel engines with selective catalytic reduction to reduce emissions. Its purpose is to clean up the exhaust gas on a vehicle before it is emitted into the atmosphere.

Last month, Sheetz also reduced diesel prices by 50 cents per gallon through the end of the month at each location that sells the fuel type.

Last September, Sheetz celebrated Truck Driver Appreciation week by offering a discount on diesel, lowering the price to $4.49. At the time, the national average cost for a gallon of diesel was around $5.06, according to AAA.

In November, Sheetz reduced the price of Unleaded 88 to $1.99 a gallon as a way to relieve some of the spending pressures of holiday driving. Last summer when gas prices were at record highs, Sheetz reduced the price of Unleaded 88 to $3.99 a gallon and reduced E85 fuel to $3.49 per gallon. At the time, unleaded fuel prices were averaging around $4.84 a gallon.

The Pennsylvania-based convenience retailer operates more than 670 locations in Pennsylvania, North Carolina, Virginia, West Virginia, Ohio and Maryland.