Indeed your energy banks may or may not deplete depending on your equipment. For those wondering, you can continue to use surjectors even after your energy banks run dry, you won't explode.
I think Military Injectors work by "refunding" part of the fuel you've burned. It guess it was done before the scripting API allowed to change the fuel burn rate of injectors, so it could perhaps use an update to make it work more elegantly (I remember one could see the fuel in the gauge "bump" - or was it Fuel collector).
But yeah, those OXPs are kind of informally mutual-exclusive, unless you think infinite fuel is fair