ALTOONA, Pa.—Sheetz is lowering the price of its diesel exhaust fluid (DEF) to 99 cents a gallon through the end of the month at select locations, reports WTAJ.

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. With the new price, drivers can save between about $15 and $75 when filling their DEF tank, depending on its size.

Earlier this month, Sheetz announced it had reduced diesel prices by 50 cents per gallon at each location that sells the fuel type. The promotion runs through the end of the month.

The average price for a gallon of diesel is $4.66, up almost $1 from a year ago when the average was $3.68 a gallon, according to AAA.

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.