Diesel fuel has to be periodically filtered ("polished") by passing it through cans of dessicant. It removes accumulated water and prevents bacterial growth. There are also biocide additives but they just _extend_ the periods between maintenance.

That's also why it's not a great idea to use diesel for your backup home generator. It will go bad sooner than you expect, and then you're left with drums of gunk that you can't dispose and can't use.

And gasoline won't help you either. It goes bad even faster.

Propane tanks are the best option they can sit in storage indefinitely.