Leaded fuel WILL harm the o2 sensor - but it takes a fairly long time. They are only good for 100,000 miles at best on unleaded, and should be replaced as a service part at that point anyway.
How long will they go on leaded? We don't know yet, and are looking for documented evidence on this. For now, we recommend if you are planning a lot of miles in unleaded countries, think about carrying a spare. Failure is evidenced by poor running, stumbling, and general rich symptoms. Replacement is not difficult.
Re the filters, K&N insist you use their filter oil and cleaner - so you have to carry both, and lots of it. The foam filters can be cleaned in fuel/gas/petrol, and washed finally in soap and water, dried, and oiled with preferably foam filter oil, but motor oil will do fine. It takes very little - a film can full will easily do a wash.
I use a foam filter myself on our G/S around the world and have been very happy with it. It's still perfectly good.
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Grant Johnson
Share the Dream!
at:
www.HorizonsUnlimited.com