The old gas degrades over time it should not be added because it has already lost it's combustibility.

Mixing old gas with new gas. Diluting new gas with an older patch increases the concentration of various compounds in it that were oxidized. Gas begins losing its combustible properties and leaves behind a varnish as soon as 30 days after purchase. There is another trick that one of your uncles or perhaps your father knew about when it came.

Even 10 year old would probably fire up ok, at least on fuel injected engines where the system is more or less closed. Old and new gas should not be mixed for a variety of reasons, the major ones are; Old gas and gas reconditioning yes and no.

Unleaded gasoline at a few years of age is no longer properly gasoline and won't combust inside an internal combustion engine of the design in any automobile,. 1 year old fuel will be fine if the can is properly closed. If you only have a half of tank.

It is not okay to mix old gas with new gas in a lawn mower. I figured i'd use it's electric fuel pump and pump the old gas into a container. When you add new gas to a tank that has old gas in it, the two ages of gas will mix and still be usable for your vehicle.

Mixing old gas with new gas is normally not an issue for most vehicles. The old gasoline mixed with the new gas, will then lower an entire tank’s combustion ability to such a level, that it is no longer a concern. I am going to do a minor service on it and the gas is probably 2 maybe 2 1/2 years old.