Two years ago I bought a kerosene heater and about 5 gallons of kerosene. I never touched either one until a few days ago. I guess the kero is bad because the heater won't work. It was stored in a closed container in an open-sided shed. The heater was new, still in the box. I want to get new kerosene but how should I dispose of the old stuff. Also, I thought kerosene lasted longer than two years?