Hi,
I thought I would comment on this. Yes, it is a very polarised subject. I believe that polarisation is due to misinformation and poor maintenance procedures.
1.Some performance air filters may let more particulates through, others will perform as good as a good quality stock paper element filter. Some stock paper filters are not too good either.
2. The MAF will probably get dirty after a period of time whether you have a K&N filter or a paper filter. I will say that if you over-oil your K&N then this may cause the MAF to require cleaning sooner however according to K&N they have tested for this and the test showed it does not happen. If your MAF is dirty or coated with something check your filter and air box etc for leaks.
3. A K&N filter requires periodic servicing, which is low in cost but requires some time. A paper filter requires periodic replacement which is fast but high in cost and not environmentally friendly. This is the reason dealers do not like serviceable air filters, because they require time to service them. This is good if you are a home mechanic (arent all rangie owners?

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4. The K&N filter will allow more air flow and filter as well due to better design. I will say that there are conflicting test reports on the filtering efficiency. Who do you believe? well that is the question of this topic. More air flow is probably not noticeable on stock unmodified rangies. Personally I did notice a very slight seat of the pants improvement and a very slight mileage improvement but in defence of my stock filter I would say it was a bit clogged (it didnt look bad though) (Dealer was supposed to replace it! hmmm) I believe that a properly maintained K&N will provide the same engine protection as a paper filter.
5. What is vitally important with both types of filters is that they seal correctly when installed. That needs to be checked and done carefully.
6. A K&N filter is a lot more expensive so it will take quite some time to realise any cash benefit when you buy a K&N. I figure about 4 stock filter changes which is equivalent to the cost of the K&N. (calculated on the filter cost from my dealer and what I paid for my K&N) Stock filter replacement interval is 24,000 miles (40,000 Km), that's 160,000 Kms before you are even.
My personal view is that the paper filter is too expensive so I fitted a K&N. I will be doing the services anyway. If you are having a dealer or mechanic do the work then probably stay with the paper filter, just makes sure that they, A: use a good quality make and B: they actually change it, not just "examine" it.
Oh, and Mark, how did you get a "2001 GEMS" rangie? The "bosch" had them by 2001 and lucas was in the past.
Cheers
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