Does 2 cycle oil go bad?

[OldJeep]

Earlier today I was mixing up some 2 cycle oil for my chainsaw. The bottle of oil was about half full and it's been that way for about 4 months. It smells like lighter fluid. I smelled another full bottle that hadn't been opened but is just as old, and it smells like normal 2 cycle oil - almost like fresh asphalt. Why does the first bottle smell like that? Did it go bad or something? It looks like it might be thinner too, but that could be my imagination.

Thanks

 

[Blue99]

2 cycle pre-mix oil usually has a bit of solvent in it to keep the additives in solution & help the base oils mix with gas.

The more volatile components could evaporate off & I suppose the odor would be different. But going "bad" from bacterial growth or oxidation would probably require several years of "opened" shelf life.

An opened container of 2 cycle mix should have a similar shelf life as an opened quart of 10w-30 oil. Keep the cap screwed on tightly.