There is one problem with old furnace oil tanks not being mentioned. The bottoms do tend to rust out from the inside. Condensation and the occasional bit of wet fuel leave water in the bottom of the tank. The tank is rusting from inside so it looks fine from the outside until it finally rust right through and leaks all over your basement.
If you are considering using diesel power you are better to put a new tank outside.
You should consider draining or pumping out the fuel in the tank you have and getting it out of your basement before it empties itself on your floor.

Consider also that diesel does rot in storage. There really are bacteria that break it down.