swaprec

mins = 10 -- this is the wait time between each swap

usedFuel = 0
while(usedFuel < turtle.getFuelLevel()) do
    startFuel = turtle.getFuelLevel()

    -- pick up charged REC
    turtle.select(1)
    turtle.dig()
    -- pick up used REC
    peripheral.call('back','teleport')
    turtle.dig()
    -- place the charged REC
    turtle.place()
    -- place the used REC
    peripheral.call('back','teleport')
    turtle.select(2)
    turtle.place()

    usedFuel = startFuel - turtle.getFuelLevel()
    if(usedFuel < turtle.getFuelLevel()) then
        for i = 1, mins do
            term.clear()
            term.setCursorPos(1,1)
            print("Running...")
            print(" ")
            print("Fuel cost per loop: " .. usedFuel)
            print("Current fuel level: " .. turtle.getFuelLevel())
            print(" ")
            print("Mins since last swap: " .. i-1)
            print("Mins until next swap: " .. mins+1-i)
            sleep(60)
        end
    end
end

term.clear()
term.setCursorPos(1,1)
print("swaprec: Not enough fuel to continue")
print(" ")
print("Fuel cost per loop: " .. usedFuel)
print("Current fuel level: " .. turtle.getFuelLevel())