Mine

function digTunnel(int)
  torch = 0
  while int > 0 do
    if turtle.detectDown() then
      turtle.digDown()
    end
    while turtle.detect() do
      turtle.dig()
      sleep(1)
    end
    if torch == 8 then
      turtle.select(2)
      turtle.placeDown()
    end

    turtle.forward()

    torch = torch + 1
    int = int - 1
  end
end

i = 64
n = i
fuelLevel = i * 3 + 3
while n > 0 do
  digTunnel(i)
  turtle.turnRight()
  digTunnel(1)
  turtle.turnRight()
  digTunnel(i)
  turtle.turnLeft()
  digTunnel(1)
  turtle.turnLeft()

  if turtle.getFuelLevel() <= fuelLevel
    then turtle.select(1)
    turtle.refuel(3)
  end

  if turtle.getItemCount(16) > 0 then
    n = 0
  else
    n = n - 3
  end
end