paying for gas


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When most people look for a gas station, the first thing they think of is the price. Just visit any Costco gas station, and you’ll see long lines that’ll take you back to the 1970s oil crisis (OK, it’s not that bad). But the cheapest gas isn’t necessarily the best for your engine. In 2016, AAA compared TOP TIER gasoline (fuel that meets higher standards) to normal gasoline and found “significant differences” in quality. Given the many rumors on and offline about Costco gasoline and TOP TIER fuel, we spoke to an expert at AAA and scoured the web to find out if the wholesaler’s fuel is worth the wait and what a TOP TIER designation means.

What is TOP TIER Gasoline?

The TOP TIER designation is the gold standard when it comes to fuel. According to AAA’s 2016 research, “non-TOP TIER gasolines caused 19 times more engine deposits than TOP TIER brands after just 4,000 miles of simulated driving.” What’s more, using TOP TIER gasoline could even clean a vehicle’s engine. Why?

Gasoline that meets TOP TIER standards includes extra additives and/or detergents that do two things: 1) they create fewer engine deposits when burned, and 2) they prevent additional deposits from forming, according to David Bennett, manager of repair systems for AAA.

Buildup is harmful because it could lead to improperly seated valves and engine misfires that, if they happen often enough, internally damage the engine and other downstream components. And in the short term, carbon buildup can reduce fuel economy, as it can alter the combustion chamber’s seal, Bennett explained. If it’s not a sealed system, “you’re not getting the actual power” when the fuel combusts.

TOP TIER does come at a higher price, though AAA found that the average difference was only around three cents per gallon in 2016. In short, filling up with TOP TIER gas is worth it.

Intake Valve ComparisonPhoto credit: AAA

Where Did TOP TIER Gasoline Come From?

The TOP TIER designation emerged in 2004 after some of America’s top automakers (BMW, Honda, Toyota, etc.) created a fuel standard that went beyond the Environmental Protection Agency’s regulations. While any retailer can apply for a TOP TIER designation, the organization behind the certification conducts random audits and lab tests to determine eligibility. Here’s a full list of TOP TIER brands.

Is Costco’s Gasoline TOP TIER?

Costco is one of around 50 TOP TIER brands in the country. So yes, Costco gasoline is worth the fuel frenzy because it’s cheap and better for your engine than non-TOP TIER fuels.

Apart from the added detergents in Costco gas, the wholesaler also conducts regular station maintenance, according to its website. That includes changing fuel filters so they catch particles before they reach your engine and taking chemical samples of the stations’ tanks “at least weekly” to check for contaminants.

That said, it’s somewhat of a mystery where Costco gets its fuel. “Costco buys fuel from major refineries and distributors in each area,” the wholesaler’s website reads.

The Bottom Line

It’s worth filling up with TOP TIER gas because it’s proven to be better for your vehicle’s engine and efficiency. Plus, it might not be more expensive if you’re a Costco member and can visit one of the wholesaler’s stations. Otherwise, check TOP TIER’s comprehensive list of certified gas stations — ARCO, Chevron, and Exxon are just a few. 

Frequently Asked Questions

What is TOP TIER gasoline?

TOP TIER gasoline is fuel that meets higher standards compared to normal gasoline that’s only cleared by the EPA. The primary difference is that there are more detergents in TOP TIER gasoline, which leads to less carbon buildup, better fuel efficiency, and a more reliable engine.

Is TOP TIER only available as premium gasoline?
No. If a gas station has earned a TOP TIER badge, then all of its fuels have been certified.

Where can I get a list of TOP TIER gas stations?
Find a list of licensed brands on TOP TIER’s website.

Is TOP TIER gasoline more expensive?
Only slightly. In AAA’s 2016 study, TOP TIER gas was three cents more per gallon on average. 

Does Costco offer TOP TIER gasoline? Is Costco gas good?

Yes, Costco gas is TOP TIER, and it’s better than its non-TOP TIER rivals. According to Costco’s website, the wholesaler “contains five times the EPA detergent requirement.”

Where does Costco get its gas?
We don’t know. According to its website, they buy gas from major refineries in nearby areas. 

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