Ethanol gas, winter blend

I don't know if Ethanol is part of the mix for you when talking about winter formulated gas but I don't believe it is here since we can buy non-ethanol winter gas. I do know for reformulated winter gas, lighter, low-boiling-point components are added to the gasoline to increase volatility. This makes your car easier to start and accelerates converter light-off, thus lowering emissions.It's all about lowering emissions in the colder heavier air. In my real world measurements, winter gas provides lower mpg's and that's in every vehicle I've ever owned.

We also get winter formulated gasoline here and also have an ethanol choice.

Edit: Check out this article on Gasoline Blending

 

Should I buy premium unleaded for my prius or will regular suffice?

 

From a MPG perspective, neither Gen I nor Gen II Prius got any better mileage on Premium, with some tests indicating a minor drop off compared to Regular. From a Horsepower perspective, Premium offered some advantage in hill climbs.

I am not aware that these tests have been run on Gen III, it is a new (to the Prius) engine.

I am happy with Regular.

 

I'd stick with the recommended 87 octane.

 

ya, there is still winter formula gas. in WA, we have same all year e-10. track your mileage. you most likely went to winter fuel sept 30 or soon thereafter. it varies from region to region. Sept 30th is our "first official frost day" here.

all summer long, i was averaging (mind you this is the MFD) 62-64 mpg. current tank is 59.5. so i have definitely lost some mileage here.
driving patterns have changed slightly due to the fact that i am using 2010 to commute to work, but that only means i am using gas faster. the type of driving has not really changed much.

now, the change in weather i feel accounts 2-3 mpg, the rest is change in gas. we still have some days that are very mild, but still not getting the mileage i was before.