Seasonal Fuel Blends: What's the difference between summer and winter fuel?

Is it OK to blend fuels from season to season? What's the difference between summer and winter fuel?
Published 12/03/2012 11:47 AM   |    Updated 06/14/2013 12:12 PM

Depending on your state's regulations, there could be up to a 30+ blend of fuel each year depending on the outside temperature. Purchase fresh fuel for your lawn and snow equipment in smaller quantities and just prior to using it for the season. It is not recommended that fuel be used from the prior season. (This applies to all fuels with 10% ethanol or less.)

Winter fuel is blended to have a higher amount of vapor coming off the fuel. This helps winter equipment start in cold temperatures. However, this also causes the fuel to age quicker and if the fuel is not treated with a fuel stabilizer it will start to break down after (approximately) 30 days, causing the carburetor to plug.

(This is a common scenario between winter seasons when untreated fuel is left in the fuel system.)

Note: Winter fuel will breakdown at an accelerated rate, if not treated, when the temperature starts to rise in the spring of the year. So, winter fuel will work in summer engines because it is very highly volatile due to the high amount vapor coming off the fuel.

Summer blended fuel will give off far less vapors and is designed for warm weather equipment use. Summer fuel has a longer life span with less need for a stabilizer. Summer fuel doesn't work well in winter equipment when trying to start an engine in 30 degree weather.

Note: Fuel stabilizer is also recommended for summer fuel, due to its detergent additives that help to keep the fuel system clean at all times.

Source: http://ariens.custhelp.com/app/answers/detail/a_id/434/related/1