The gas will continue to oxidize for years, eventually turning into a sticky varnish. Definitely add more Sea Foam and take the car for a drive, so the treated gas gets into the fuel injectors, intake valves, top piston rings and exhaust valves. You almost can't add too much Sea Foam, so I'd put 4 oz. per gallon. Adding STA-BIL simultaneously will only help, without any chance of harming the engine.

Different brands of gasoline will oxidize at different rates. Cheap, no-name gas can begin to oxidize in three weeks. Name brand, "top tier" gasoline is usually good for one year without any extra treatment.

Why not burn off the 1/4 tank and start with fresh gas? Also, store the car with a full tank because the gas tank will rust in the exposed areas.

Back in the early '90s, I drove an F-150 pickup truck that had been sitting for over a year with an untreated tank of gas. After 200 miles, the oxidized gasoline contained enough varnish to stick all the intake valves in the open position. The engine of course would not run until a mechanic removed the valve covers and hammered the intakes valves back-and-forth with solvent to free them again.

The gas will continue to oxidize for years, eventually turning into a sticky varnish. Definitely add more Sea Foam and take the car for a drive, so the treated gas gets into the fuel injectors, intake valves, top piston rings and exhaust valves. You almost can't add too much Sea Foam, so I'd put 4 oz. per gallon. Adding STA-BIL simultaneously will only help, without any chance of harming the engine.

Different brands of gasoline will oxidize at different rates. Cheap, no-name gas can begin to oxidize in three weeks. Name brand, "top tier" gasoline is usually good for one year without any extra treatment.

Why not burn off the 1/4 tank and start with fresh gas? Also, store the car with a full tank because the gas tank will rust in the exposed areas.

Back in the early '90s, I drove an F-150 pickup truck that had been sitting for over a year with an untreated tank of gas. After 200 miles, the oxidized gasoline contained enough varnish to stick all the intake valves in the open position. The engine of course would not run until a mechanic removed the valve covers and hammered the intake valves back-and-forth with solvent to free them again.

By contrast, I stored a 1980 Cutlass Supreme in a barn in the mid-'90s. In that case, I added an entire bottle of Marvel Mystery Oil to a full tank of gas and sprayed a little down the throat of the carburetor until blue smoke came out the tailpipe. After two years undisturbed, she started-up immediately and ran perfectly for an entire Summer before I sold it.