if you remember this table [a breakdown of typical costs for 1 jump or 2-weeks’ ship operation] you’ll see it includes fixed costs (mortgage, life support, maintenance) plus variable costs (fuel):

assuming 2 jumps per month;
each = 2 weeks in jump space & 1 week at destination, eg R&R and sourcing passengers / cargo CR
Mortgage
111,000
Life support ( – Blaxton 5%)
21,000
Maintenance cost ( – Blaxton 10%)
2,700
Fuel (refined)
22,000
/2 jumps per month =
c. 77,700 / jump

now then…

the table assumes 2 x purchase of refined fuel (approx cost Cr500/ton) / month.

but you do not have to purchase refined fuel.

 some starports (eg type A & B) may have both refined & unrefined fuel for sale
 some starports (eg type C & D) may have only unrefined fuel for sale @ approx Cr 100/ton
 some starports (eg type E or X) may have no fuel for sale
 you might be able to skim fuel from gas giants or oceans, or crack it from ice using your ship’s fuel skimmer (& maneuver drive, in the case of cracking)
o you would then use your fuel processor to refine the fuel
o skimmed or cracked fuel is of course free

1. the following is approx ship’s costs for 2 weeks’ operation using purchased, unrefined fuel:

Fuel (unrefined)
4,500
/2 jumps per month =
c. 60,200 / jump

2. the following is approx ship’s costs for 2 week’s operation using FOC unrefined fuel:

Fuel (unrefined)
0
/2 jumps per month =
c. 55,700 / jump

NB: - using unrefined fuel to power your jump drives is dangerous
- regular & through scrubbing & maintenance of fuel skimmers and processors is essential
- if the system has no gas giant nor water / ice, you must purchase fuel (usually from the starport)
- if the system government will not allow refuelling from gas giant/s or ocean/s or ice cap/s (common in heavily-trafficked systems, eg starport type A or B), you must purchase fuel