Do gas stations in AZ sell winter mix / blend gas, or is it different depending on where it is sold? I am wondering if the refineries mix all of it this time of year because they don't where it is going to be sold. I like the Maverick station near me because they sell the non-ethanol blue gas.

Beside the ethanol free stations, I've never heard of any fuel being referred to as "winter blend".

Is that just a lower ethanol percentage?

https://newsroom.aaa.com/2013/06/what-is-the-difference-between-summer-and-winter-blend-gasoline/

Winter gas is more volatile and evaporates more quickly, so it is ideal for it is used in the colder air of winter. In terms of gas mileage, you get better mileage on summer blends than winter blends because the summer blend gasoline has about 2% greater energy value than winter blend

I think I might have found my own answer:

Unique Gasoline Blends

The Phoenix metropolitan area, including Maricopa County and parts of Pinal and Yavapai Counties, is required to use special gasoline blends during the winter and summer to meet federal air quality standards. Tucson also uses a special blend during the winter months. The rest of Arizona, outside the metropolitan Tucson and Phoenix areas, uses conventional gasoline year round.

Arizona’s special blends are credited with improving air quality in the Phoenix and Tucson metropolitan areas. Industry analysts and refiners, however, claim these unique blends are expensive to produce, in part because expensive blend stocks and sophisticated equipment are necessary to produce the specialized blends and the number of refineries that produce them is limited.

There is a winter blend at the maverick in Payson.

The winter blend is supposed to help get rid of the lingering cloud in the valley during winter months.

I don't drive any of my vehicles enough to notice 2% one way or the other.  I probably wouldn't notice 10% either.  I do mostly in town driving, at about 60 miles a week. A tank of gas in my Civic could last a month...

Interesting

Years ago someone that worked at ADEQ told me the cloud was due to particulates comprised mainly of tire rubber from our vehicles on the roads/highways.

Wonder if if we will ever know the true reason.