If an engine is sitting for decades...

[SteveSS]

...would you expect to find some gas in the engine oil? Or is that a problem that needs to be addressed?

 

[69 Sleeper Bee]

Whatever was gas isn't gas anymore after sitting for decades.

 

[RemCharger]

5qts of oil here is $24 at wally world here

 

[Don Frelier]

Only if the fuel pump diaphram failed and it syphoned in there.
I suppose it's possible from a carb but very unlikely.