What to do with Old Gasoline

I bought a gasoline generator for my home because of frequent power outages. Wouldn’t you know: after I installed it we have not had a single power outage that was worth getting the thing going. So now I have about 15 gallons of 5 or 6 year gasoline in the garage. I know engines do not run well on old gas. The only way I know of to dispose of it is to run the stuff through the car. Is there any problem running gas this old in the car? How much can I run through at a time, filling the rest of the tank with good gas?

Your gas will be very stale by now, even with Stabil added. I would not put it in the Buick. Here we have a disposal site at the town dump; it has a large tank for used oil and one for gasoline and diesel. I would try the landfill first. Most cities have some facility for this type of waste.