Service Issues: Good dirty filters.

[skyship007]

This is a quote from an air filter company expert on why you should not change an air (Or oil) filter too early and I thought it might be of interest to some forum members who like clean filters.

"Ninety percent of the lifetime amount of dirt that passes through a filter does so in the first 10 percent of use."

Any filter has an initial efficiency rating and a final efficiency rating. The initial rating is done after the filter has had 20 grams of either fine or coarse grade dust applied at a specific flow rate based on the maximum flow capability of the filter. The final rating is taken when the filter reaches 20-25 inches of water restriction at that flow. A filter could start out at 97 percent initial efficiency and end up at 99.9 percent on the final. The final figure is the one touted during advertising. Typically, by the time the filter has reached 20 percent of its lifetime, efficiency has improved 1-3 percent. This is why changing an air filter too early causes more dirt ingestion than changing it a little late. Changing your air filter too often is killing your engine with kindness, more or less. A one percent increase in filtration efficiency is a 50 percent decrease in contaminants passing thru the filter.

I knew something about filters before I started doing some more reading on the subject, but even I was surprised at the figures for the air filters and can fully understand why the engine long-life fanatics in Bobs the Oil Guy forums, pay great attention to air and oil filtration.
One of them said he never fits a new air filter but bribes a chap in a local garage to give him a moderately dirty used one when his is so bad his idle rpm drops. I definitely would not recommend that procedure as I am not sure what happens with the V40 engines as it could effect the mixture. Does anyone know if it causes a check engine warning as it does on some cars???
Never forget there is a slight risk of a non Volvo filter falling apart from old age, so if you want to keep your oil in good order, think about your air filter change schedule, because a non functioning air filter will contaminate the oil.
It will be interesting to see if my UOA (Used oil analysis) results show a big decline in Silicon contamination as my air filter gets dirty, as it's no good at the moment because it's still too clean. One of the big reasons why the Nissan truck mentioned in the Blackstones site did 122,000 miles without an oil & filter change, was because the air filter was not changed. If the Nissans original 15 year old air or oil filter had been changed it never would have survived such an un-planned experiment without damage.