I run Costco gas all the time. It's actually pretty good.

 

There is 110 all over here.

 

From what I know it is Top Tier Gasoline which is same used by some 76 Stations.

I use it.. No issues

 

It's good to know that no one is having issues with the Costco stuff as I plan to run it in mine when I find the right one.

 

For what it's worth, we previously had a tuned car on the dyno and were experiencing abnormal timing pull. After checking the ignition system and verifying there were no issues, the owner mentioned that he had used Costco gas (used Chevron previously). After filling with a fresh tank of another brand, the timing pull was gone. I have seen this a handful of times through customer data logs, so I would just say it depends on the vehicle's level of tune. For the highest performance, I would recommend sticking to the Chevron's and Shell's. For cars that are stock or just used for weekend fun, you shouldn't notice much of a difference.

 

In our area, BP offers 93 octane at most stations, but ironically it is not a "Top Tier" fuel. I cannot run it in my CIS 5.6L Benz V8 - there is some additive missing that the old V8's miss. [no pun intended] I go down the street to Quik Trip, which is a Top Tier fuel, but they peak at 91. Note: In my newer cars, BP fuel causes no problems.

 

Slik560's comment caused me to check on if Costco was a "Top Tier" gas. According to Costco it became such a fuel in March of this year.

As our valued member, you expect Costco to always offer the finest quality products at the best possible price. Gasoline is no exception. Costco has closely studied fuel additives and engine deposits, and conducted extensive engine tests at nationally-recognized laboratories. As a result, we decided to increase the detergent additives in our fuel to provide a better value to our members. As of March 2014 Costco is listed as a TOP TIER™ gasoline retailer.

I've been using Costco fuel for a couple years in two mildly tuned daily driven turbo Subarus without issue, but admittedly, I haven't been logging data on the Subies to see if my car's ECU is pulling timing. Both cars are running about 50HP/80Tq over stock and seem to run great. Fuel economy is better than what the fed says it should be too, but that's likely the efficiency of the ECU tunes, rather than the gas in the tank.