(WCMH) — Convenience store chain Sheetz has lowered prices to a steal for the Fourth of July holiday weekend, but not all cars are eligible to take part.

A statement sent out on Monday, June 27 by Sheetz said all of its stations would cut the price of unleaded 88 gas to $3.99, and ethanol 85 flex fuel to $3.49, effective immediately.

The price for unleaded 88 is almost $1 lower than the national average, which sits at $4.88 as of Tuesday, June 28, according to AAA. Meanwhile, Virginia’s average price for regular unleaded gas is $4.70.

The prices for other fuel types, however, weren’t mentioned in the press release. A photo taken by WFXR’s sister station, WCMH, at an Ohio Sheetz indicates they did not get the same deal, with unleaded 87 still standing at $4.77 per gallon.

Unleaded 87, 88 and E85 are just three of several common types of gasoline, with unleaded 89 through 94 all showing up in various other gas stations, according to the U.S. Department of Energy.

The numbers stand for the octane rating of the gas. The U.S. Department of Energy says the rating can tell how well the fuel will resist engine knocking, which is when fuel burns unevenly in the engine and potentially causes damage to the engine’s cylinder and pistons, according to Firestone Auto Care. Most cars can use unleaded 87, but some luxury cars require higher-grade gas types to work with their high-performance engines.

The U.S. Department of Energy breaks octane ratings down as follows:

  • Unleaded 87 – Regular grade gas
  • Unleaded 88 through 90 – Midgrade
  • Unleaded 91 through 94 – Premium

Specifically, Sheetz says the following kinds of cars can use its unleaded 88 gas:

  • Cars made in 2001 or later
  • Light-duty trucks
  • SUVs
  • Flex fuel cars

The best way to know what kind of gas to use in a car, according to the U.S. Department of Energy, is to check the car’s owner’s manual to see what octane rating the manufacturer recommends using.

However, the government agency also says while gas rated lower than the manual requires can damage a car’s engine, it’s possible to use gas at a higher octane rating than what the manual says.

“For most vehicles, higher octane fuel may improve performance and gas mileage and reduce carbon dioxide emissions by a few percent during severe-duty operation, such as towing a trailer or carrying heavy loads, especially in hot weather,” the agency wrote. “However, under normal driving conditions, you may get little to no benefit.”

E85 flex fuel, the other gas at a discount with Sheetz, is specifically for cars labeled as being able to use flex fuel. The U.S. Department of Energy said a common way to tell if a car is flex fuel-approved on models after 2008 is to see if it has a yellow gas cap, or an “FFV” or “Flex Fuel” badge on the car’s body. However, the government agency also said a flex fuel car using E85 instead of unleaded 88 also gets anywhere from 15 to 27% fewer miles per gallon.

Sheetz said its dramatically lower price points for unleaded 88 and E85 are intended to reduce pain at the pump for Americans, and that the offer would be valid through the Fourth of July holiday travel season.

View the map below to find a nearby Sheetz location.

The Pennsylvania-based company has more than 640 locations across Pennsylvania, West Virginia, Maryland, Ohio, Virginia, and North Carolina.