Costco winter gas - poor mpg?

Hey Folks,

I haven't given much thought to gas quality and I'm still getting to know this truck, however lately I have been giving a lot of thought to gas mileage.

I'm not much of a number cruncher and I haven't been very diligent with tracking my KM's to Litres. However I know that I usually get around 425ish KM on a tank, and that's with about 12 litres left.

Lately I've been filling at Costco because it's close and usually about 5 cents cheaper. After my most recent fill, I noticed my MPG was suddenly very poor and I had to re-fill before 350km. On suspicious of gas, I filled at Shell and I'm now on track for one of my best ever mpg/tanks.

Highly anecdotal at best. But a little googling seems to suggest that Costco gas especially the winter formula has lots of ethanol and can be a cause of poor gas mileage.

I'm assuming Costco must have recently switched over to a winter formula? Anyone else notice a sudden big difference in their gas?

I did recently have a o2 sensor replaced, but the extreme drop was a few fills after.

 

I usually get 425 kms when the light comes on , but I haven't used the Costco gas , but my best mileage has always been with the Shell 91

 

Costco and Sam's/Walmart are going to run a higher ethanol content since it's a cheap octane booster.

I've had Costco summer gas "turn" in 3 months stored in jugs for my dirtbike.
Dad used to have a 5 gallon jug for the mower that he'd refill maybe once every 2 years back in the 70s.
Back to my dirtbikes, Chevron holds for 6 months without problems.

 

gotta love that winter blend....
I have had this problem with my 2010 Subaru... the 12taco seems to be less picky....

 

I get gas at the same places all year long...... WaWa and Turkey Hill.

Winter gas blends are different than summer gas blends.
http://auto.howstuffworks.com/fuel-efficiency/fuel-consumption/summer-fuel1.htm

My truck will lose 2mpg every winter....no matter what gas I use. I will run 17-18mpg in the summer and 15-17 in the winter. And no...it does not have anything to do with 'warming' the truck up.

For some reason, I think Toyota's (our trucks - or atleast mine) gets worse mileage in winter. My husbands Acura isn't affected by the gas. ????

 

I fill up at Costco exclusively;
http://www.fuelly.com/driver/vicali/tacoma/fuelchart

Strikes and gutters

 

I'm not up on winter/summer gas but I keep track of my mileage and when I switch over to winter tires it goes from 23-24 down to 19-20 MPG. My winter rubber is Toyo Open Country MTs 245/75/16. Summer I run Yokohama Parada 265/50/20's. I always buy gas at the same co-op. My Taco is a 07 extra cab 4x4 V6 6 sp. I run the tires at the same pressure winter/summer so I'm guessing the difference may be the rubber compound and the tread design. This pattern has repeated for 3 years now and the change happens with the first fill up after the tire swap. That's my 2 bits worth.

 

My truck is an 07 and is totally stock.....and I've had it since new.

Every year / winter ...doesn't matter where I get my gas or what tires I've been running (on my 2nd set of tires)....the mileage always drops 2-3mpg with the winter gas. Doesn't matter what octane I use or what tire pressure I run...... I'm accepted it 'as normal' for this truck. And believe me, I don't understand it either. I've never had a vehicle that was affected by gas like this one has.