Pasted

function canRefuel()
    return turtle.getItemCount(16) > 0
end
 
function fuelUp()
    local oldSlot = turtle.getSelectedSlot()
    if (canRefuel()) then
        turtle.select(16)
        turtle.refuel(1)
        turtle.select(oldSlot)
    else
        print('Error: no fuel')
    end
end