Mining Turtle Obsidian

-- This is for TurtleOS 1.5 and prior.
while 1 do
    turtle.dig()
    os.sleep(0.5)
    turtle.forward()
    os.sleep(0.5)

    if turtle.getFuelLevel() < 10 then
        local i = 1
        while i < 17 do
            turtle.select(i)
            turtle.refuel(1)
            i = i + 1
        end
    end
end