Only if they are so old you won't even want to think about eating them.
Gasoline is a homogeneous mixture.
Gasoline is a mixture not a chemical compound.
No, a coin can not float on gasoline.
Gasoline is a mixture of several hydrocarbons and various additives.
Yes, gasoline starts to go bad when it is about 1 month old. After 6 months you should not burn it in an engine unless you have put a fuel stabilizer in it. In that case it will be usable for about 8 months. This is also important with small gasoline engines on lawnmowers for example. Bad or old gasoline can damage a small engine very easily.
Nope, adding new gas to old just makes a larger batch of bad gas.
Nothing. 4 month old gasoline is still good enough to use. Gasoline starts to go bad after 1 month but can be used up to 6 months after it was refined.
Gasoline will turn an orange color when it goes bad and it will also have a foul odor. New gasoline is a clear with a slight tan color.
yes
yes
Gasoline is old after a month. Especially gasoline which contains ethanol. Ethanol looses its octane rating much faster than petroleum.
There are many things that can cause gasoline to go bad. Time (decrease in volatility), oxidation, or water contamination are all culprits.
Old gasoline turns varnish like and coats injectors and spark plugs and gums up carburetors. you should dilute with lots of fresh gas or siphon out the old.
Sure.
Gasoline loses much of its volatile components to evaporation, and also slowly oxidizes. Gas can "go bad" and become unusable as soon as 4 to 6 months after dispensing from the pump. Keeping it in a tightly sealed container will help prevent oxidation. There are fuel stabilizing chemicals that can keep small amounts of gasoline usable for up to a year or possibly longer.
drain your tank