Ethanol has a bad habit of absorbing moisture, It will even accumulate moisture on a humid day. Once it gets saturated enough, It will separate from gasoline.
Fuel School: Phase Separation in Ethanol Blended Gasoline

 

Having spent many years in "service stations", yes we used to perform services, I talked to many tanker drivers. They told me how it works at the tank farms. All tankers pull up to the refill ports and get their fuel from the same tanks. The difference in the manufacturers i.e. Shell, Chevron or Cheapo is the key they use to activate the additives. There is a large board with many key slots all labeled according to their drop location. The driver just uses the correct key to fill his truck and bill the farm owner. All in one move.

Usually when there are problems with fuel at one location it is the location's lack of maintenance on their in ground tanks. We used to stick the tanks every day and keep track of any water build up.

If you live in a cold weather area it helps to run a bottle of gas de-icer through the tank once in a while to clear out any water you might have picked up in someone's in ground tank. That is the usual culprit.

Hope this helps.

xfirepops

 

Costco's Response to Top Tier Gasoline Inquiry

Top Tier Gasoline

All gasoline retailers in a given market sell the same grade and quality fuel, as the government has very precise standards for octane and other gasoline characteristics. The only difference between different brands of fuel is the detergent additive package. Since 1995, the federal government requires that all gasoline sold in the U.S. contain detergent additives. These additives must be EPA-approved, and the government specifies the amount based on what it takes to keep engines free of deposits. Because it's a performance-based requirement, over the years the fuel suppliers have figured out ways to use less of these expensive additives to achieve the government standards. All Costco gasoline contains detergent additives in the amount necessary to meet these requirements.

Recently, several automakers (BMW, GM, Toyota, and Honda) announced their new "Top Tier" standard for gasoline, as they believe the government additive requirement is too low. They invited gasoline manufacturers to certify their fuel to this higher standard, and several have done so. Other major oil companies, such as BP, declined as they believe the auto manufacturers are simply trying to reduce their warranty claims. To achieve this voluntary "Top Tier" designation, all the fuel sold in the U.S. must meet the higher standard. Costco cannot currently do this as we buy from a variety of refiners and distributors around the country and do not own our own truck terminals where the additives are blended with the fuel.

Nor is it certain how much additive is really necessary to keep an engine clear of deposits. The fuel detergent is only one component, as anything that causes incomplete combustion will lead to valve deposits and fuel injector clogging. It's easy for an auto mechanic to simply declare the problem is the gasoline. So the science is uncertain, and the industry response is certainly not unanimous. Regardless, we are actively researching the issue directly with the various additive manufacturers. We are hesitant to raise the cost of fuel to our members without first understanding if this is simply a way for some brands to charge more for their fuel. We do know that we sell a tremendous amount of fuel with very few complaints.

Costco only buys fuel from reputable suppliers, and we do a very good job of maintaining our tanks and pump filters to assure clean fuel is delivered to our members. If you remain concerned about fuel deposits, Costco sells a four-pack of Chevron's Proguard fuel injector cleaner in our warehouses for about $10, or $2.50 per bottle. It's much less expensive to use a bottle of this occasionally than to buy higher priced fuel every time you fill up. Any auto parts store has a shelf full of similar products.

Again, all Costco fuel contains detergent additives sufficient to meet the government standards. As with anything we sell, our fuel is 100% guaranteed.

--------------------------------

Also, Top Tier gasoline retailers:
Top Tier Gasoline

 

No problems with Costco gas here in Upstate SC. I haven't used any premium grade as I usually fill my truck or 'pocket rocket' there with the regular grade. But I do try to stay away from any station (cut rate or premium brand) if I see the fuel delivery truck on the lot. I'm convinced that pouring that new gas into the storage tanks just stirs up any deposits and/or condensation. All stations are suppose to have filtering on their delivery systems. But filtering out crud or deposits is a lot easier than removing condensate or moisture. And I doubt that the cut rates (and maybe the premium) stations have fuel /water separators on site to address any moisture acumulation. So I avoid filling up when they are taking deliveries.

And I do use HEET during the winter season, especially if any of my cars sit for an extended period. Otherwise, a can of fuel system cleaner every 4 months or so is routine for me in all my cars.

As neoprobity & xfirepop both stated above, the gas all comes out of the same pipe! And remember, once you get 4 ft below ground level, the earth's temperature is fairly constant around 45-50 deg F. That's why tanks are typically placed underground. Surrounding soil acts as an insulator, which reduces the likelihood of condensation accumulating due to large temerature swings. So it's only a matter of preference on which additive package you like best or your perception of how 'clean' any local station operates their tank system.

 

Based on personal experience and research, I suspect there is a nationwide problem with the quality of Costco gasoline. In other words, Costco sells "bad gas." Moreover, Costco is aware of this problem but has failed to remedy it. As a result, a number of consumers have sustained damage to their vehicles as a result of Costco's "bad gas." On January 28, 2015, I filled my 1989 Ford Econoline van with Costco regular gas in Simi Valley, California. My van has fuel injection and starts immediately. However, on this occasion, it took several minutes with about 10 attempts to start my vehicle. A passerby said it was probably the Costco gas. Later that day, I started my van again, but the startup was delayed. I suspected Costco gas as the culprit. I put in $20 worth of Shell gas and my van started much better. The following day, my van started but there was minor backfiring in the exhaust. I then went back to Shell to add additional "good gas" so as to completely fill up my gasoline tanks. (My van has 2 tanks.) However, I could not start my van afterwards. An automotive garage nearby came to my rescue. They were able to start my van by spraying brake fluid into the intake manifold. Based upon extensive diagnostic testing, the mechanic has concluded that contaminated fuel from Costco caused my vehicle's mechanical damage. I am looking at $1,000 in repairs. (I informed Costco about this problem and was advised to submit an incident report which I shall prepare.) An Internet search has revealed a number of consumers who have been damaged from Costco's "bad gas." (I also recall last year that a late-model vehicle at the Fremont, California Costco was unable to start after filling up with Costco gas. Could it have been from Costco's "bad gas"? Shortly later, the underground gasoline tanks were replaced with new tanks!) Consequently, I believe this problem is ripe for a class action lawsuit against Costco and I would be willing to be the lead plaintiff. Thank you.

 

In general i buy mostly gas from Sam's Club (87 for most, 93 for the Crossie & Judge) but sometimes will by from Hess (close and about the same price - they have 89 which I'll sometime blend with a half tank of 93 to make 91).

Have not had any problems in near thutty year. Do remember bad gas in Michigan and Indiana but not here. Maybe just lucky or maybe the stations I go to have a high turnover rate.

 

Locally, that is the only gas I buy and never had any problems in several years as a costco member. My cars run great on Costco gas.

 

Please research Top Tier Gasolines

Top Tier Gasoline

Costco is a Top Tier Gasoline Retailer. I am not sure when this occurred. I have been using Costco Gas exclusively in my Crossfire with no problems.

 

Gasoline is called a fungible product. It's properties are regulated by each state. The only difference in brands is the additive package. Any station can have dirty tanks with water etc., or get the wrong gas in the wrong tank such as E85 in a regular tank etc.

 

Costco and BP are on the top tier list at Top Tier Gasoline