Gas spoils rather quickly, it has many problems including varnishing. However, a simple and reliable product can help in this matter greatly.
STA-BIL:
STA-BIL keeps fuel fresh
Fuel that is stored either in the can or in the engine fuel tank, starts going stale after a little more than a month, resulting in hard starting, poor performance and reduced engine life.
When added to fresh fuel, STA-BIL Fuel Stabiliser stops the formation of gum and varnish in fuel system components. It contains corrosion prevention additives to fight the damaging effects of Ethanol in fuels and cleans fuel injectors and carburettors restoring performance.
Marketed for over 40 years in the USA and recommended by more than 100 engine and equipment manufacturers. STA-BIL is safe to use in any petrol engine and will not harm any engine or fuel system components or catalytic converters.