I'm using Red-Ex, no sign of valve seat wear as yet, i.e. valve clearances not closing up. Has anyone had experience of that stuff you put in your tank and it lasts for - I think - tens of thousands of miles. I think it may be Bardhal, Bardahl, something like that, not sure, though. Or can anybody suggest something else? I like the idea of something long-lasting so that I don't have to forever dosing every single tankfull. My bike is an '82 airhead.