Heavy fuel oil *spoilers*

[SoundsOfNight]

So it took me 3 playthroughs to realize that your car's fuel canister has a use - but I sold it wayyyy before I found this out.

Is there any other way to get additional heavy fuel oil? I can't seem to buy it back from the pawn shop.

If not, is there a way to edit my save file? It's going to drive me crazy having this quest outstanding, especially because I'm a Conceptualization / Actual Art Degree-type char.