They are good filters for road use, they give better air flow, but they are made of cotton and you have to oil them, they simply clog up with dust, you would have to wash it out with petrol each day and re oil it to be effective, once it clogs up, basically you get black smoke all the time which means a fuel rich mixture in the combustion chambers leading to elevated head temperatures. I didn't know Ken had one fitted until nearly at the end of the trip and I think Matt knocked some of the crap out of it, but I think some damage must have occurred internally by then. I can't use a K&N filter anyway as the oil used is corrosive to the air flow sensor in the Td5, Mahle paper filters are what I use, I used 3 in Morocco.