High amounts of oxygen in ethanol blended fuels cause gasoline to decay faster, and if left standing for long periods of time, the decaying fuel leaves varnish and sludge deposits as depicted in these carburetor images.
Gasoline and milk are both organic -- they decompose the same way. A foul, sour smell indicates BAD GAS!
Power equipment not treated with an ethanol fuel stabilizer will become hard to start within 30 days. Gasoline will decay in as little as 60 days!
Gasoline has a very short shelf life and will start to go bad within 30 days. Gasoline is in one of three stages of life: Good, marginal, or bad. Depending on the age of your gasoline and which stage it is in will dictate which product to use. Ethanol Shield is designed to keep fuel fresh and ready to use. If the fuel is marginal Mechanic in a Bottle will allow the fuel to run in the engine without causing harm