As the others have said it won't clean your intake valves (looking at your question there was no mention of cleaning valves anyway )
So, as it will clean your whole fuel system and combustion chamber then it should improve mpg. Saintsteve had it done and it did just that. His emissions were much better afterwards
Why is it when someone mentions terraclean everyone immediately thinks you are doing it to clean your valves?
True...why don't we stop offering up extra info and see how much wiser we become.
It's a related item. If OP didn't know what these engines can be like for carbon build up he does now and he now knows why it's reported as not effective for these engines. I'd consider it a waste of money if every other part of my intake system was clean and I knew I still had intake valves/chambers that looked like an open face coal mine. VW tech bulletin confirms loss of power etc as an effect of this.
'So, as it will clean your whole fuel system and combustion chamber then it should improve mpg. Saintsteve had it done and it did just that. His emissions were much better afterwards' It doesn't clean the whole system though does it.
So despite Terraclean confirming that it's only good for an injector clean and SaintSteve advising 'save your money' it was a completely pointless addition to the thread.