Is Costco Premium Gas 91 Or 93 Octane? (And Does It Even Matter?)
We have to separate the chemical "octane" from a fuel's "octane rating" since they can be two different things. Think about it this way. If you learned your shapes in kindergarten, you should easily recall this rule: All squares are rectangles, but not all rectangles are squares. Now let's apply this maxim to the chemistry of gasoline: All octane compounds raise octane ratings, but not all compounds that raise octane ratings are actually made from octane.
Case in point, both ferrocene and ethanol will increase the rating, but won't show up to any octane family reunions. Lead will do the job, too, but comes with a few downsides, such as behavioral, learning, growth, reproductive, cognitive, hearing, memory, muscle, and joint problems.
And here's why we care about octane. Most cars subsist on a "regular" 87-octane diet, but high compression or forced induction (turbocharging or supercharging) engines need octane ratings nearer triple digits. Lofty pressures and heat inside these tightly squeezed combustion chambers ignite low-octane fuel unevenly, resulting in detonation (bad for you, great for a mechanic funding his kids' college).
So when you pull your Bugatti Chiron (or other high-performance or luxury car) into a Costco gas station, stick with 93 octane to provoke every one of the car's 1,479 horses into action. Also, smile for pictures since Bugatti sightings at Costco stations are probably rare. But should you refuel your quad-turbo W16 warp drive with 91 octane, the engine will limit itself to a paltry 1,200 horsepower to avoid harmful detonation.
Now, Costco's Frequently Asked Questions page states that its fuel ratings are "typically 87 octane for Regular and 91 octane for Premium Gasoline." The word "typically" is a problem for you Chiron owners because you'll have to research which extra-long-hose Costco gas stations can unleash all 1,479 ponies.
Finding Costco gas stations that count to 93
Life would be just that much better if Costco's website listed which of its stations featured the more premium premium, but alas, it does not. Costco's site does show which U.S. states have Costco warehouses and how many there are (606 as of this writing), though not all warehouses sell gas (only about 67%). Simply finding a list of all Costco gas stations (or Kirkland, the brand Costco uses for its fuel) is a maddening endeavor. Your best bet is to use Costco's warehouse list to find nearby stations and call them if your engine really needs premium gas.
Even determining which states offer widespread 93 octane is tough. According to find93.com, which documents user-reported sightings of 93 octane, 46 states sell 93. Take this list with a boulder of salt, though, because it includes California, and that state will not sell you 93 octane for street use. To understand why, simply reverse time to October 2001 and navigate to Autoweek.com on your beige Compaq Presario to enjoy a new article titled, "No More 92: Premium Octane Rating Drops in California."
The article reports that Gov. Gray Davis banned octane-boosting and cancer-causing methyl tertiary butyl ether (MTBE) in 1999, but the only real alternatives were using ethanol, which couldn't be added in the same proportions as MTBE, reducing octane ratings to 91, or adopting Unocal's MTBE/ethanol-free patent-protected process for creating 92 octane, which would have meant licensing fees for refineries. Ethanol clearly won, as evidenced by the fact that in 2001, about 1 billion bushels of corn went into ethanol production, and by 2010, that figure skyrocketed to 5 billion bushels. Over 20 years later, 91 still reigns supreme and there's no 93 at your average California gas station.
Octane exceptions
In some states, such as Florida or Virginia, the top offering can be either 93 or 91 depending on the station. If you go a Wawa in a 91/93 state, you might find both at the same pump, but Costco only offers "Regular and premium gasoline, and diesel at select locations," so you'll never find an 89 mid-grade or other octane options there. At Costco you get two choices, and if the top choice is 91, then that's what you get. You might even find 92 octane like it's California in the 1990s.
And 91 isn't even the wimpiest high-octane choice, as Alaska doesn't sell anything higher than 90 octane, which is below the bare minimum for premium as defined by the U.S. Energy Information Administration. Don't bother calling one of the three Alaska Costco Warehouse locations with gas pumps — their 90-octane high-mid-grade won't be able to get your Chiron up to its reduced 1,200 horsepower. Maybe just rent a car at Costco and leave the Chiron at home.
If you're shy about calling your local Costco for octane ratings, know that Yelp contributors often take pictures of the pumps. The first picture in the Yelp review for Hoover, Alabama's Costco clearly shows a button for 93 octane premium. After you're done checking out the pics, you can enjoy oddly glowing reviews for the atmosphere of a filling station, such as Laura S's comment that, "I love the gas station attendants! They are always so super nice and love chatting!"
If you needed to know where you can get 93 octane and a great conversation about how much your favorite college football team disappointed you last weekend, here you go. Just don't take your Bugatti Chiron or the conversation will be constantly interrupted by looky-loos.
