Many people flock to warehouses like Costco and Sam’s Club with high hopes of getting the best deal on the price of fuel and although both places offer similar savings, there’s a stark difference in the quality of gas they pump.

The most notable difference between Costco and Sam’s Club is that one provides Top Tier gas while the other does not.

A study written by Consumer Reports stated that, “Not all gasoline is created equal. There is plain old regular, and then there is regular gasoline that meets a higher standard, known as Top Tier.”

Top Tier is recognized as a high-quality fuel performance specification in fuel that was developed by some of the leading automotive and heavy-duty equipment manufacturers, according to Top Tier’s website. Top Tier gas can reduce build-up deposits on fuel injectors and on intake valves. This can restore engine performance, vehicle responsiveness, and fuel economy.

In 2016, AAA conducted a study that revealed that Top Tier gasoline keeps engines 19 times cleaner.

In response to increasing levels of carbon deposits in modern engine designs AAA reported that the Environmental Protection Agency mandated a minimum level of detergent for all gasoline sold in the United States in 1996. Top Tier fuel is gasoline which has more detergent additives than the Environment Protection Agency requires. Detergent additives help keep engines clean.

Costco offers Top-tier gasoline with higher levels of required detergents; however, Sam’s Club does not provide Top Tier gasoline.

Continued fuel use without the Top Tier additive package could result in 2% to 4% lower miles per gallon, increased emissions, and a greater chance of maintenance issues, according to AAA.

Even if a person buys fuel outside of a warehouse station, CarFax reported that, “Yes, Top Tier gas is worth the extra money. The benefits are not a myth.”