When I fill up at Costco or Sams, I always use Premium at these locations I have not seen a difference in mileage vs when I use 87 or 91 at Chevron, 76 or Shell the only difference I see is on my credit card statement…
Not very scientific, but I've driven 5,312 miles on 113 gallons of Costco gas and 5,913 miles on 127.8 gallons of other brand gas. Of those miles, 7,341.5 were on a trip from Phoenix to Yellowstone, Glacier and Green Bay leaving 3883.5 miles around Phoenix. I don't hyper-mile, I just drive the car. Costco mpg - 47.0 Other brand mpg - 46.3
California is EPA/CARB reformulated gasoline. The clean burn recipe is basically lower energy content and no MPG differences would be expected between brands or grades. The only thing you can do is get TopTierGas.com for adequate additives and Costco is TopTier member as well os others. Once you get to AZ or other places there could be more variations.
On average 50 cents higher price for chevron, with the same amount of ethenal, tested myself, Costco gas is the best, and I bet the delivery truck is the same one.
As 10% ethanol blend(E10) prices collapsed in late 2014-early 2015, in the Pacific Northwest, Costco's price for the brew really led the hallmark plunge in Washington state & Oregon, along the I-5 corridor. Possibly, Costco prices in other regions also were low. Now tho, as prices have bounced up, Costco gasoline is NOT necessarily the low price leader. Costco is still a good deal....... specially with its 3% rebate at year's end. A past post of mine, remarked of excellent mpg for one of my tanks of Costco E10. Following tanks tho, indicate mpg ratings similar to other E10 tanks that I have long term & accurately calculated for 3 gasoline vehicles, as being 8%, 7%, & 5% less than tanks of 100% gasoline(E0), for which I also have long term accurate calculations.
Based on what I know about statistics, unless you're measuring MPG under laboratory conditions, your margin of error is a bit too wide to be making any meaningful claims, based on a fill-up or two. One way to compensate for this is to make a habit of measuring it every time you fill up; plotting it over time, and the increasing sample size will eventually reduce your margin of error to within tolerable limits.
Reviving this old thread about Costco gas, in particular, my post above, which I stand by. In an earlier post in this thread, someone told of major fuel injector problems after gassing up at a Costco, possibly inferring too much ethanol may have caused the problem. As reported in my above post, one tank of Costco gas almost gave as good MPG as my usual complete burning of ethanol-free gasoline(E0). Possibly one explanation could explain both stories of tragic engine problems & my tank of excellent MPG. There have been quite a few court cases, that indicate the accidental double blending of 10% E10 gasoline resulting in E20 & even accidental blendings as high 60+% that were sold as 10% ethanol blends. Now my spectacular Costco 10% (E10) MPG could easily be explained that Costco may have missed blending ethanol into 100% gasoline, accidentally resulting in actual E0 gasoline & not E10 gasoline. As stated, mis-blendings, both too much & no blending at all, could easily explain both the bad & good results of poor blending processes.
This isn't necessarily an accident. Logistic and other supply issues and constraints can sometimes lead to substitutions, usually temporary. When done in the direction of an upgrade, it falls under 'no harm, no foul'. It is the forced or undisclosed downgrades that lead to court cases.
I've had a spectacularly good tank too, and also suspect it was 100% (regular) gas. If it is in fact doing this much good to mpg, why the heck are we where we are...
Nah! Double blendings (& even worse blendings to 60+% ethanol in gasoline) are not logistics, supply & substitution issues, as the court rulings against gasoline distributors indicate. At best, they are mistakes. At worst, they are purposeful actions by distributors to meet yearly blending rules.
The "ethanol in gasoline industry" has poured lobby money into the fed gov't for 30+ years. They used unfounded arguments that ethanol decreased national oil consumption & burned cleaner. First, it is obvious that blending 10% ethanol into gasoline blends that leads to 8% to 5% LESS MPG can't save oil, since it also takes oil to produce ethanol & support the "ethanol in gasoline industry". Second, 114 octane ethanol can't burn clean in designed 87 octane gasoline engines. 114 octane ethanol might burn clean in designed 114 octane ethanol engines, but INDY ethanol engines are not being raced in the INDY 500 series to burn clean. People would never allow 114 octane racing gasoline to be used in their 87 octane gasoline engines. But people are forced to use (not burn efficiently) 114 octane ethanol, blended into 84 octane gasoline to make designated 87 octane gasoline blend(E10).
I was replying to the non-blending case you seemed to have experienced, not the multi-blending cases.
I have been a believer in using E0 since late May, when I had a P0171 occur in my Prius. Swapped MAF, checked PCV, even replaced intake gasket, all to no avail. Did a check of the E content of the gas in the tank and found it to be E25, from a Walmart Grocery gas pump. Topped off with E0 and haven’t looked back. It helps with the warmup penalty. If I don’t sit in my car at lunch the mileage stays around 47 mpg. If I sit in the car or have to defrost it in the morning, I’m in the low 40’s.
Update to past years of previous data: Now, I have had five 87 octane gasoline engine vehicles in a row, using decades long 10% ethanol blends(E10) AND ethanol-free gasoline(E0) in separated use, that show 87 octane E0 MPG to be 8%, 8/%, 8%-7%, 7%, & 5% better than 87 octane, 10% ethanol blend (E10) MPG. Presently, my Washington state has 300 E0 gasoline stations. Other states have far more E0 stations (Wisconsin-936, little 87 octane E0, tho); Southeast U.S.A has ~ 40% of all U.S./Canada E0 sources (much 87 octane E0). Some states, no E0 stations.
Still nay! People who know their cars, weather, & driving conditions, can tell the difference between E0 & E10, even in the short term. Of course, long term records (like mine) readily bring out the difference between E0 & E10.
Yes, it is easy to get kits that measure the percentage of ethanol in one's gasoline tank. & yes, you got a double blending(PLUS) of E10. In a post above, I remarked about getting one tank of Costco E10 that gave almost as good MPG as E0. But, I also had tanks of E10, that gave MPG less than my accustomed E10 tanks(even with consideration to weather & driving conditions), in which I suspected excess ethanol above 10%. Unlike you, I have never had crippling tanks of E10, altho my old 1988 Ford Festiva NEEDS E0 to run smoothly.
Some youtube videos show people burning e0 and e10 with e10 leaving unwanted residue to piston surfaces. Sure it burns clean regarding atmosphere pollution but it just fills volume in place pretending that you're getting more quantity from the pump with the ethanol and e0 combined. I prefer carrying less fuel volume at e0 than more fuel with e10 in the tank, more dense energy in smaller volume any day. It's also in politics where certain voters in certain states that grows corn can earn more money from corn if their corn are processed into ethanol for fuel so certain politicians will get more votes from those corn ag states. Also raises corn prices due to artificial shortage of corn being used on "many applications" for ROI purposes.
One fuel truck jockey I spoke with said Costco uses their own top tier add pack, then mentioned not understanding the economics of them supplying such. He also mentioned how every retailer/distributor will refill from the same local spigot in remote regions, offering an example of a refilling station in the Redding area of Northern California.
