Regular vs. Premium Gas: Do You Need Premium?

Updated November 13, 2026

Premium gasoline costs noticeably more than regular, so it’s worth knowing when you actually need it. The short answer: use the grade your vehicle’s manufacturer specifies.

What octane means

The octane number on the pump measures a fuel’s resistance to “knock” – uncontrolled ignition of the fuel-air mixture in the cylinder, which can make a pinging sound and, over time, harm the engine. Higher octane does not mean more energy or more power by itself; it means the fuel tolerates higher pressure and temperature before igniting on its own.

EIA classifies the grades by the antiknock index shown on the pump: regular is 85 to under 88, midgrade is 88 to 90, and premium is above 90. In high-altitude regions such as the Rocky Mountain states, each grade may be sold at a lower octane rating, because engines need less octane in thinner air.

“Required” vs. “recommended”

• Premium required: the engine is designed for high-octane fuel (often high-compression or turbocharged engines). Use premium; lower grades can cause knock, reduced performance and possibly damage.
• Premium recommended: the engine can safely run on regular because its computer adjusts timing to prevent knock, usually with somewhat less power and possibly slightly lower mileage. Whether premium is worth the extra cost is your call.
• Regular specified: premium brings no benefit. The engine cannot take advantage of the extra octane, so you’d be paying more for nothing.

The requirement is in your owner’s manual and often on the inside of the fuel door.

How big is the price gap?

The difference between grades changes over time. You can see this week’s national and regional prices for regular, midgrade and premium side by side on our home page and on every state page. EIA notes that the gap between grades has generally widened since 2006.

Common myths

• “Premium cleans your engine.” All gasoline sold in the U.S. must contain detergent additives. Some brands add more, in every grade – the grade itself is not what determines cleaning.
• “Premium gives better mileage in any car.” Only engines designed or tuned for it can benefit.
• “Midgrade is a compromise worth buying.” Only if your manual calls for it; otherwise it is simply more expensive regular.

Further reading: EIA: Octane in depth and fueleconomy.gov.