Originally Posted by Steve Ownby
Gary, have you seen any data on the K&N heavy duty line?
Yes, I have read their website data claiming an overall efficiency of 96% dust removal. That is about the same as the oiled foam 'air cleaner' on a cheap Brigss lawn mower engine.
In the world of real air cleaners, 96% efficiency is a whopping failed part. Donaldson, Baldwin, Fleetguard all use 99.4xx% as the bottom threshold of an acceptable air cleaner performance.
Put another way, for every 100 ounces of dust that the K&N will see, it will allow 4 ounces through.
Real air filters receiving the same 100 ounces will allow 0.6 ounces through. In reality, these real air filters typically perform at the 99.9xx% overall efficiency. Frequently, we saw returned Fleetguard air filters that reported in at 99.980%. It is not uncommon at all. These would have passed 0.02 ounces.
An ISL, ISC can be dusted with about 5 ounces dust. ISB about the same or slightly less.
K&N and another brand (AFE?) have as a product feature the re-usability aspect for sure. But as you can read above it comes at a great cost. A tip to anybody looking to buy a pre-owned MH, if it has had this type of air cleaner....keep looking or plan to get the price down enough to pay for the at minimum in-frame overhaul needed to fix the dusting issues.
Speaking of dusting, the bad news besides the obvious need to rebuild or replace the engine is that it does not show up immediately. There is usually enough time to trade it off before anybody notices the increased oil consumption and high blowby. In fact, you could consider getting the engine tested at a Cummins distributor to see what the blowby is on the MH you are considering. Not sure if a dealer or owner will like that but you can guess how important that is to you.