Q - What is Bambi?
A - Viable Target
A possible problem I see with using Vaseline or other "fuel" is this is essentially just a small diesel engine, if the fuel ignites like it does in a full size diesel the pressure produced could be substantial. The piston could be ejected with great force.
Nemo ME Impune Lacessit
Manus sapiens potens est
пиштоли не убиваат луѓе, тие само го прават тоа полесно
Oh, didn't think of that. haha Good thing ya'll brought it up before someone ended up with an aluminum rod stuck through their palm!
ETA: And I was about to suggest adding an oxidizer to deal with the running out of oxygen thing!