Drain old degraded gasoline from the tank, and replace it with fresh gasoline. When storing a vehicle, treat the vehicle's fuel system with stabilizer by mixing the stabilizer with gasoline to prevent oxidation during storage.
Gasoline is a refined product that contains components that evaporate over time. This causes an inability of old gasoline to properly combust, resulting in decreased engine performance or the inability to start an engine with old gasoline. Discarding old gasoline and replacing it with fresh fuel typically corrects the problem. Identify old gas by observing and smelling it; the appearance of old gas is darker than regular gas, and it smells sour. It is best not to store gasoline for more than a couple of months, although fuel stabilizer can help extend the life of gasoline for up to 18 months.
The hydrocarbons in gasoline react with oxygen, producing new compounds. Over time, the chemical composition of gasoline changes and causes deposits of gum and varnish in the fuel system. This results in clogged gas lines and filters and issues with the carburetor and fuel injector. Another common issue caused by old gasoline is water contamination. As a result of heat cycling, condensation can form in the fuel system. It is best to avoid gas stations with low traffic, as underground storage tanks experience changes in temperature that causes moisture to form.