Old fuel disposal or use ?

Small amounts, I catch in a glass jar and use to clean parts. If draining several gallons from my Mopars where it was sitting over a year, I add 1 gal per fillup in my M-B diesel, which some people do routinely in winter. I'll also use some in my lawnmower. If it smokes, I'm glad I didn't risk gumming up my car's fuel system.