Wallet Hacks

Costco, Exxon, Shell, Chevron, Mobil, … Which Gas is the Top Tier?

I love buying gas from Costco.

I love Costco gas mostly because it's insanely cheap. Like 20-25 cents cheaper than my local gas station (and always that cheap, according to many gas apps), which is arguably somewhat pricier than average because it's in a weird location and super convenient for people who live near the weird location.

I try to go when the warehouse isn't open, so the lines are not as crazy.

Sometimes I go and it's no wait for a pump… and when it's dark out and their lights are on, it looks like an oasis in the desert.

My Costco gas station opens at 6 AM and closes at either 9:30 PM (M-F), 8 PM (Sat) or 7 PM (Sun). That means it opens three to four hours before the warehouse. It remains open for an hour or two after the warehouse closes. That's a nice wide window when the wait will be short.

One day, for like a minute, I wondered – why is it so cheap? Is Costco gas as good as other pricier gas stations? Does it matter?

Gas is Regulated

Thanks to the Clean Air Act, the Environmental Protection Agency regulates fuel and fuel additives used in cars (and other engines) because burning gasoline contributes to pollution.

The actual regulation is 40 CFR Part 80 (“Regulation of Fuels and Fuel Additives”): subparts A (general provisions, applying to all 40 CFR Part 890 fuels programs), B (controls and prohibitions), C (oxygenated gasoline), D & E (reformulated gasoline), G (detergent gasoline program), H & O (gasoline sulfur) and J & L (gasoline toxics).

Sexy huh?

The point is that with respect to the gasoline itself, it's all pretty much the same.

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It's All About The Additives, Baby!

What about the additives? These detergents?

These are also EPA approved and there is a certain amount that each company must add to their formulation. They're added so vehicle engines don't accumulate carbon deposits and lose efficiency. If you sell gasoline in the United States, you are subject to these rules.

Where things differ is when companies do more than what is required.

Top tier gas! It's the toppest!

In fact, when the EPA announced the minimum gasoline detergent standard in 1995, many companies were putting more than what was required… so they started a “Top Tier” designation. Actually, it's an industry standard so it's TOP TIER™ – all caps, trademarked, the whole nine.

The Top Tier designation is not associated with the EPA but is controlled by the industry. To get the logo, you need to meet their specifications.

Who sells gasoline that qualifies as Top Tier? (official list, as of August 2018)

  • 76
  • Aloha
  • ARCO
  • Beacon
  • BP/Amoco Ultimate
  • BP Regular
  • BP Silver
  • Breakaway
  • Break Time
  • Cenex
  • Chevron
  • Circle K
  • Conoco
  • Co-op
  • Costco Gasoline
  • CountryMark & CountryMark Plus
  • Diamond Shamrock
  • Esso
  • Express Mart
  • Exxon
  • Fast Fuel
  • Fast Stop
  • Hele
  • Holiday
  • Irving Oil
  • Kirkland Signature Gasoline
  • Kwik Star
  • Kwik Trip
  • Kwik Trip Express
  • Mahalo
  • Marathon
  • Metro Petro
  • MFA
  • Mobil
  • OAAI
  • Ohana Fuels
  • Petro-Canada
  • Phillips 66
  • PUMA Energy Caribe
  • QT
  • QuikTrip
  • Ranger
  • Reeder's
  • Shamrock
  • Shell, Shell (CA), Shell (PR)
  • Sinclair
  • Sunoco Ultratech
  • SuperAmerica
  • SuperFuels
  • Tempo
  • Texaco
  • Tri-Par Qwik Stop
  • Valero
  • Win Win

Most of the major gas companies are included.

Does it matter?

This Consumer Reports article seems to think so.

They cite an AAA report that studied the difference between Top Tier and non-Top Tier gasoline. They discovered that non-Top Tier gasoline left more carbon deposits.

Here's the difference in an intake valve run continuously for 100 hours on a cycle meant to replicate 4,000 miles of real driving:

That one on the right looks about 19 times dirtier!

How much more do you pay for this better gasoline? It's not likely you do.

Local price competition has a greater impact on price than the additives. Gas stations just off a highway are more expensive than those farther from the exits. Those near a Costco will be cheaper than those farther away.

(Many years ago, I'd get my gas at an Exxon that was a mile away from my Costco because there were never any lines. It was always two cents a gallon more but saved me a good ten minutes of waiting time – an easy trade.)


Costco Gasoline is better than the EPA regulations for additives and detergents.

It's also cheaper.

So go when there are no lines and win!