Sugar

function refuel()
	if turtle.getFuelLevel() < 1000 then
		for i = 2,16,1 do
			turtle.select(i)
			os.sleep(0.1)
			while turtle.getFuelLevel() < 1500 do
				if(turtle.refuel(1) == false) then
					break
				end
			end
		end
	end
end

function unload()
	for i = 1,16,1 do
		turtle.select(i)
		os.sleep(0.1)
		if i == 1 then
			if turtle.getItemCount(1) > 1 then
				turtle.dropDown(turtle.getItemCount(1)-1)
			end
		else
			turtle.dropDown()
		end
	end
end

f = io.open("speed.dat","r")
if f ~= nil then
	speed = tonumber(f:read())
	f:close()
else
	speed = 0.8
	f = io.open("speed.dat","w")
	f:write(tostring(speed))
	f:close()
end

ticks = 750
f = io.open("ticks.dat","r")
if f ~= nil then
	ticks = tonumber(f:read())
	f:close()
end

while true do
	turtle.select(1)
	if redstone.getInput("front") then
		--Calculate speed
		speed = 1800 / (ticks+1)
		f = io.open("speed.dat","w")
		f:write(tostring(speed))
		f:close()

		--Refuel and unload
		refuel()
		if turtle.getFuelLevel() < 300 then
			print("fuck im out of fuel")
			os.reboot()
		end
		unload()
		ticks = 0
	end

	--Check Forward
	if turtle.detect() == true then
		if turtle.compare() == false and redstone.getInput("front")== false then
			turtle.dig()
		else
			turtle.turnLeft()
		end
	end

	--Check Down
	if turtle.detectDown() == true and turtle.compareDown() == false and redstone.getInput("front")== false and redstone.getInput("right")== false then
		turtle.digDown()
	end

	turtle.forward()

	ticks = ticks + 1
	f = io.open("ticks.dat","w")
	f:write(tostring(ticks))
	f:close()

	os.sleep(speed)
end