Homer3D

I recently got a Costco membership about a month ago. I have been filling up my daily drivers with Costco gas. While filling up I see these signs for 5x Detergent in their gas, improved performance, etc. Stuff you would see boasted about with Top Tier gas. So I came home and looked it up online. Costco's website prominently shows the Top Tier logo
http://www.costco.com/gasoline.html

And you can see here they are on the list of TOP TIER Gasoline Retailers
http://www.toptiergas.com/retailers.html

When did this happen?

EDIT: I just found the answer to my question. Looks like it just happened according to their website. At 10 to 20 cents less per gallon than the local Chevron here, the Corvette is getting Costco gas going forward.

Neil Baker

I don't see Sunoco on the list. Why?

AORoads

Maybe top tier is an advertising/marketing program? And that's why Sunoco doesn't participate? As to Costco, up until just a short while ago, they never wrote on their gas receipts about all the additives they were adding which could mean many things. Such as, previously, they were adding the bare minimum required. Now, there's all this mumbo-jumbo at the bottom of each receipt. I'm fairly certain it's a good thing. Maybe.

vatakle

i believe costco uses 10% ethanol in their gas. When i use their premium gas in infiniti g35, i get 1-2 mpg less than when i fill at Chevron. I guess my driving pattern is more or less the same as it is used for commute. I am still gonna stick to Chevron/Shell for corvette.

Anyone is aware if Chevron/Shell uses 10% ethanol too?

KX

Yes indeed, Costco gas has 10% ethanol. I never do a full fill up there, just a top off of 3 to 5 gallons. I do believe I get better mileage with another brand of premium fuel.

Nosferatu

I can tell you this, I have an Evo X in the garage with a custom turbo and tune. This car is VERY PICKY in what fuel it'll take before it'll start showing knock. I use Sam's Club gas in it and it runs like a champ. Since then, I've been using Sam's fuel in my Vette. Cheaper and works.

zero11

I'm sure they all use a blend of ethanol in their gas ,I will stick to big name brands in my area.

TRSCobra

I typically fill my DD (2012 Mazda 3 Skyactiv) with shell, but the first time I used costco gas, I noticed my average fuel economy went from ~37.5 to 39. Thought it must have been good traffic or I was easier on the throttle than normal, so I went back to shell and saw my normal 37-38 average. Last week I went by costco and filled up, and once again, I'm seeing <39 mpg.

I'm starting to think this may not be just a coincidence.

LDB

This is about the time of year when refiners are switching from winter blend to summer blend gas. The difference is vapor pressure, and the thing that is manipulated is percent added butane. Butane isn’t very dense and thus doesn’t contain as much energy. All other things being equal, winter gas with more butane for higher vapor pressure will give about 3-5% lower mileage. So it is possible that you are still getting winter blend gas at Shell, while your Costco station has switched to summer blend. Of course, that explanation wouldn’t make sense if you are still seeing the difference in another month when all will be on summer blend.

To forestall a couple of added questions, the reason most people probably don’t notice this difference is that air conditioners don’t run much in the winter, and they also cost some mileage. So the inherently lower mileage of winter blend gas is not noticed because air conditioners are not robbing mileage in winter. And no, this is not an oil company conspiracy to rob consumers in the winter. Cars need higher vapor pressure gas in winter to compensate for lower temperatures when the engine is started from cold. Without the extra butane, cold engines wouldn’t run very smoothly for the first few miles on cold mornings.

TRSCobra

Had the first costco tank been recently, I would agree with you, but my first tank was in early January, so I doubt they were running summer blend. I won't be regularly using costco gas anyway, as it is farther out of my way than my usual shell station. It is something I will continue to keep an eye on when I do make costco runs, though.

seong

Thanks for the good info. I heard there was difference between winter gas and summer gas, but didn't know what the differences were. Now I do, thanks to you!!

About Costco gas: I never went to Costco gas station, because someone told me their gas wasn't as good as name brands like Shell. After reading this thread, I may give it a try. (not with my vette, but with my DD)

PatriotZ

Jeeze....Been using Costco for years (08) in my Z since new....no problems....almost 40,000 miles....That was before I "got educated" on using the correct gas...Hmmmm, Now that I am educated... Think I will switch to Costco....Ha
I am waiting for the guys who "always put regular gas in their Vettes" cause ....well it is cheaper and they are saving money....to chime in.

cv67

Yeah that extra 2.00 per tankful oughta bankrupt a person

airmed2

I'll bite. I get a kick out of statements exclaiming "no problems...almost 40,000 miles." How scientific is that? What then does it mean for someone who has used regular and hasn't had any problems in 40,000 miles?

This reminds me of my snowmobile ownership and breaking it in. Several state that doing it the Motoman Method has given them no problems and their sled is fast. Who's to say that following the owner's manual break-in method wouldn't provide the same result? Unless you have two identical cars/vehicles/whatevers... and drive them exactly the same while altering only the item(s) being tested, one cannot conclude that doing it this way over that way was better.

(Yes, I know this is a revived thread)

Jon

Zero_6

Manual said to pump premium but didn't say which brand.

owc6

Any of the Top Tier brands are just fine for the car. The site lists all brands that qualify. They also explain what it takes for a brand to be listed, which is more than just the level of detergent.

http://www.toptiergas.com

billyboy47

I'm surprised citgo and Sunoco aren't on the list.

orca1946

I'm sure different station use different blends all the time to make there gas "better" in some way to advertise it that way.

Zero_6

Thanks Lisa. I'll be pumping Shell and BP.

SladeX

http://pure-gas.org/

I used this site to plan my trip to Bowling Green and South Carolina.

I'm more for using non-ethanol, low sulfur gas.