I have filled gas at Costco, and BJ's for years, even before getting the new Prius. BJ's gas gives me improved mileage. Better then big brand names. Costco probably has multiple distributors. The one costco close to home(1 mile away) always end up giving me bad mileage(calculated mileage 48-49). There is one on way to work(about 10miles away). Gives me better mileage(calculated mileage 52-53)
...if you live in a Refomulated gasoline area, you are stuck with a lower energy content (lower MPG), which EPA believes is a cleaner E10 blend for metro areas with smog/ozone issues. If you are outside of RFG area (inner Dallas may be RFG but nearby regions may not be) then you could see higher MPG non-RFG fuels but no guarantee...it can vary. But if you see a pattern develop that may indicate some stations may have a certain supply situation more or less favorable for Prii MPG. Previously I have posted a map so you can see where RFG is used also on EPA website they give county by county breakdown where it is used.
Aloha guys, just to chime in. No diff in mileage here on Maui. Costco gas here can be aprrox .90 cent a gallon cheaper than the big boys. As of this past week (Nov 10-16 2014) gas is typically $4.40 a gallon here. While at Costco it was $3.45 yesterday the 17th. But as posted, no real mileage diff. {'-'}
I'll just have to chime in on this one. Some of my best fuel economy results have been with Costco gas. However, my driving is very mixed and it depends on how much elevation change i have during a tank of gas. Costco and Mobil are my favorites, and are very consistent. Arco, which seems to be the cheapest gas (price wise), usually results in my worst observed fuel economy.
I find no difference in MPG when using Costco gasoline. I would check tire pressure, especially if there are a lot of temperature & pressure changes. By the way, Costco (along with BP/Arco) is a Top Tier gasoline.
I notice that GasBuddy.com seems to have started noting "TopTier" brands when they give you the list of stations in your area. ...well California is reformulated gasoline, so one woud think not too much difference there. Hawaii sounds good about now!...supposed to 15F tonite. Does HI have E10?
I realize this thread is about Cosco gas, but there is not any noticeable difference in ''Sam's Club'' or Shell gas in my car--- except price. I usually run the Shell @$2.59 right now---- $2.45 at Sam's. Filled there Sunday...
"Top Tier" is a trademark designed to designate gasoline with particular detergent additives specified by certain automakers to use in their engines. It may imply such, but doesn't denote a higher quality of gasoline than any other gasoline.
All gasoline comes from the same pipeline, so there is no difference in gasolines other than additives.
I'm still a bit skeptical. Although all gasolines have to meet the same government standards, I haven't seen anything to suggest that the energy content of all gasolines is exactly equal. I used to routinely measure my exact mileage from each tank of gasoline (before I got the Prius which shows it in real-time), and I saw a difference in fuel economy between fuel vendors. I'm not talking about E10 vs E15, which has a obvious difference in energy content, but grade-for-grade, some brands produced lower fuel economy numbers. I'm not a petroleum engineer, but I believe that gasoline is not a pure substance, but a mixture of many different hydrocarbons, which when blended, conform to a certain standard. Depending on the source, it may be reasonable to assume that there would be differences in energy content, and therefore fuel economy. I may be out to lunch, but I remain uncertain until I see hard data.
....take a look at this USA map of many different gasoline requirements in the US. http://www.api.org/~/media/Files/Policy/Fuels-and-Renewables/US-Gasoline-Requirements-Map.pdf We also have winter/summer blends, E0 in some areas, Regular , Mid, Premium Octane. If you want to say, within some regions, all stations get the same basic gaso, that could be correct in some regions, especially if you are in a RFG region where EPA controls the recipe.
Just curious - do they still make you use E10 gas there? Doesn't seem you would have the air quality problems the ethanol blend is required for.
I can confirm that this has also been my experience. My mileage was always measurably less after filling up at Costco, (and similar discount-gas outlets) so I stopped filling up there because the cost-saving didn't match up to the fuel economy.
I haven't filled up at a holiday or SA for a while, been doing costco. Maybe next tank i will try it and see how it goes.
...if you're outside of a USA reformulated gasoline area, there could possibly be minor variations in MPG because the energy content is not a controlled spec (octane is the controlled spec). If you are inside of a USA reformulated gasoline zone, not much variation as the EPA recipe essentially sets the energy content (lower energy content to allow for lowest emissions).
