Gasoline and diesel are commonly stored for emergencies, generators, and critical equipment. Most people assume that if it’s sealed and sitting quietly, it’s still usable. That assumption is the problem. Time changes stored fuel in ways you can’t see. The breakdown doesn’t show up on a shelf. It shows up when an engine is supposed to start and doesn’t. Shelf life matters because stored fuel only has value if it performs on demand. When it fails, there’s no...