Simple refuel

function select_fuel(from_slot)
    local slot
    local success

    slot = 1
    success = false
    while slot <= 16 do
        turtle.select(slot)
        if turtle.refuel() then
            success = true
        end
        slot = slot + 1
    end
    return success
end

function print_fuel_status()
    print("Fuel level: ", turtle.getFuelLevel(), "/", turtle.getFuelLimit())
end

function check_fuel()
    local sleeptime
    local try

    try = 0
    sleeptime = 0.5
    while turtle.getFuelLevel() < turtle.getFuelLimit() do
        if not select_fuel() then
            print("Waiting fuel... retrying in " .. sleeptime .. " seconds.")
            print_fuel_status()
            sleep(i)
            sleeptime = 2
            try = try + 1
        else
            sleeptime = 0.5
        end
        print_fuel_status()
        if try > 500 then
            print("Master forgotten me...")
            return false
        end
    end
    return true
end

check_fuel()