mine

local NUM_SLOTS = 16
local args = { ... }

function refuel()
    print("Refueling...")
    local fuelLimit = turtle.getFuelLimit()

    for i = 1, NUM_SLOTS do
        turtle.select(i)
        local reachedFuelLimit = false

        while true do
            if turtle.refuel(1) then
                if turtle.getFuelLevel() == fuelLimit then
                    reachedFuelLimit = true -- full, so stop refueling
                    break
                end
            else
                break -- slot is either empty or contains non-fuel item, so go to next slot
            end
        end

        if reachedFuelLimit then
            break
        end
    end

    fuelLevel = turtle.getFuelLevel()
    print("Refueled to " .. fuelLevel .. "/" .. fuelLimit)

    return fuelLevel
end