straight to the point:

The TARDIS Fuel Bank is way to easy to brake. I left clicked once with nothing in my hand and it shattered and because I didn't use a pickaxe, it didn't drop.

It's not that big of a deal, but I know I go around randomly clicking things 'cause I'm bored, So I think the fuel bank should be a little harder to brake

Also,  as far actually needing fuel, its a really cool idea!

problem is, Im not sure what can be used as fuel... I'll just be sat there trying to cram some cobblestone into my  fuel bank like "iS tHiS FuEl?!"

(obviously, I know cobble isnt fuel, that was slight exaggeration for comedic purposes :P )

Also, the amount of fuel that is needed seems a bit hit or miss (on DMU). I leave my TARDIS landed somewhere and the fuel goes down like, 10% (depending on how long I've left it) but like now, Ive been in flight for the entire duration of me writing this bug report (about 10 or 15 mins) and the fuel hasn't gone down at all

EDIT: WAIT! I think I get it now. The depletion of fuel inst equal to the amount of time spent in flight, right? Fuel decreases every time I land, by about 5% or 10% (Im assuming depending on the distance traveled), So the fuel consumption is equal to Amount of flights, not how Long I was in flight for

I'll make sure to have this fixed for the next update!

Also Matt covers the fuel system in one of the recent videos on our YouTube channel, off the top of my head you can use, coal, charcoal, zeiton-7 ore and block, planks, logs and toxic waste.

As yes, fuel consumption is based on how far you travel. In the coordinate travel screen there is a bit below the input boxes which shows you the estimated fuel usage for the journey