Fuel useage?

Before i start, i know this is a dumb question, so i dont need any **** about it. I also know that theres a million variables, and no real answer. Im trying to transition from doing some hay as a hobby to doing it for a living and i need to figure out APPROXIMATELY what my start up cost will be. Ive talked to friends and local guys and gotten insanely different answers. So how the heck do you figure your fuel costs? Heres what im looking at. Ive got about 60 acres im going to out into timothy. Ive been lucky and rented a bunch thats already seeded, but the ground i own needs started over. Its currently grass hay but will have been sprayed, and the ph is around 6.5. My plan is to hit it with a cultivator, but i have a row cultivator so ill think ill have to do it twice (once across and once around). Then ill go over it with a disc, broadcast it, and disc it again. Old tractors, a farmall m and an 8n ford. So how do i estimate? Also, if anyone sees a problem with my olan, id LOVE to hear it, i wont be offended, input from people with experience is extremely important.

Fuel useage?