Is all premium gas the same? | Fuel Tips

Not all premium pump fuel is created equal. “Yes, it is,” you say, “the octane rating is right there on the pump.” Well, there’s more to fuel–even premium-grade fuel–than just the octane rating.

First, the octane rating of premium can vary: East Coast consumers usually have access to 93-octane fuel, while those west of the Mississippi often receive just 91 octane.

Fortunately, many modern cars can retune themselves to accept different octane ratings. For example, the Ford Focus ST spells out the differences in its owner’s manual: 252 horsepower on 93 octane and 243 horsepower on 87 octane. “If this is a linear difference, that would put 91 octane making 249 horsepower,” explains Zachary Santner, senior quality specialist at Sunoco. “How about a 3-horsepower difference for East Coast versus West Coast fuels?”

But there’s other stuff in gasoline that can affect an engine’s performance–building blocks like, Santner notes, aromatics and olefins. EPA regulations have allowed the aromatic content of pump fuel to range from zero to 50% volume, while olefins can range from zero to 25% volume. These levels can vary depending on the brand of fuel, location of station and time of year, as pump fuels are often blended at regional terminals with the exact recipe determined by season, location, additive package and commodity prices.

“Fuels that can vary from zero to 50% aromatics and zero to 25% olefins will look and perform very differently,” Santner explains. “Aromatics are very dense and have a BTU/gallon content that is 20% higher than paraffins found in gasoline. This would mean that a fuel with 50% aromatics would be able to provide much better miles per gallon compared to a fuel with 0% aromatics.”

While it’s rare to find a fuel with aromatics at either end of the range, Santner does stress how it’s possible to find a wide variation among pump fuels–and why, when you see someone claiming dyno numbers between premium and regular fuel, other variables might come into play. (He also notes that Sunoco Race Fuels always follow the same recipe with zero variations.)

Comments

arthuruscg GRM+ Memberand New Reader
12/22/21 9:21 a.m.

There is now a trend to label 91 as premium and 93 as Premium+ or some other BS name. WTF, no Premium is 93.

z31maniac MegaDork
12/22/21 10:45 a.m.

arthuruscg said:
There is now a trend to label 91 as premium and 93 as Premium+ or some other BS name. WTF, no Premium is 93.

Some states don't have 93, so 91 is Premium, like here in Oklahoma.

Although a very small portion of gas stations have recently started selling E0 93, but it's crazy expensive. And performance gain over 91 is marginal at best.

Driven5 UberDork
12/22/21 1:02 p.m.

arthuruscg said:
There is now a trend to label 91 as premium and 93 as Premium+ or some other BS name. WTF, no Premium is 93.

Nope. Technically regular is 87, midgrade is 89-90, and premium is 91-94. Nationally the two most common premium octane ratings are simply 91 and 93, with the most prevalent differing regionally. Companies are also allowed to use other marketing names, but the grades will still fall into these octane ranges. This means they're also entitled to use naming conventions to differentiate between their multiple premium offerings.

rslifkin UberDork
12/22/21 1:08 p.m.

The grades vary a bit with location as well. Around here, it's rare to see 91 available anywhere. Most stations carry 87 / 89 / 93 locally. Some will have 90 octane E0 as well, either instead of 93 or in addition.