There's ethanol in gas year 'round. There is something different in gas in winter, that can impact mpg, but it's not ethanol vs no ethanol. It's something else, not sure exactly.
I don't have the documentation but in Washington state Ethanol is removed April 1st and put in a 10% blend of fuel November 1st. I will locate the intel as some states may differ. I cannot speak for Canada because that is another country.
Yeah check on that. I'm pretty sure ethanol free gas is not happening, year round. The stations that have ethanol free gas are few and far between. Just the first hit I googled: Summer-Blend vs Winter-Blend Gasoline: What’s the Difference?
Well that's debatable, I've never looked hard. What I do think: all the major players have ethanol year 'round, that is not what defines winter gas vs summer gas.
I use Ethanol-free gas in my lawn equipment and old tractor. Some manufacturers of equipment with 2-cycle engines specifically recommend it. Why Use Ethanol Free Fuel? Find ethanol free gas.
The one source of ethanol free gas local to me is chevrons highest octane, so no thanks lol. But the point I'm trying to make: summer has typically still has ethanol.
The EPA and its Canadian equivalent changed the way they tested the cars back in 2014, why I am unsure but all my cars have gotten better results then their posted gas milage.
Just NRC/Transport Canada for 2014. The EPA changed the testing method back in 2008. The EPA has an updated method for 2017 (something to do with the roll-down or "rolling" portion of the test). I'm not sure if NRC/TC updated their methodology to include the EPA changes.
I purchased my 2016 Prius C used, but I reviewed the previous owner's "history" in some detail. He was averaging 50-60 mpg consistently. I am *excited* that this little red car might be able to get 60 miles out of one gallon of gas. That's incredible. I also read that the EPA changed the way they calculate fuel consumption in 2008 (in America). That really does feel like a dirty trick. How do you compare these vehicles when the standard keeps moving?
They actually changed the calculation again in 2017 to better reflect expected fuel consumption. Their numbers are mainly for comparing new cars but they also publish recalculated numbers for older models too. Go to http://www.fueleconomy.gov.