The secondary filter is what is referred to as the safety filter which is the last line of defense for the engine.
Yup ........ that's
true ......
As they are a paper element filter the paper thickness is what regulates the air pressure and flow entering the engines air intake.
I would suspect that the
porosity of the filter paper is probably what actually does it ......
First and foremost please do this for my own sanity:
The inner filter MUST be changed everytime the outer filter is changed they are designed to work in tandem with the outer elelement to clean the air in two passes and cut all the dust and dirt from the air stream intering the air intake on you orange beast of burden/toy/tool/pet/critter.
Ahhhhh .... I don't think so ..... at least not on my B2910 .....
The inner filter (which is
a screen) is designed to keep boulders and other large objects, such as your bathtub, lawnchairs, and kid's tricycle, out of the engine .... it just ain't gonna do a whole lot as far as dust (dirt mebbe .... if they are large clods .....)
And Kubota
DOES NOT necessarily recommend changing the secondary every time you change the primary ....
The air filter manufacturers do not recommend blowing them out or washing them as some in the business are doing .....
Well, that might depend on which manufacturer you are talking about ......
But at any rate,
they are in the business of selling air filters now aren't they ?
as it compromises the integrity of the air filter construction and weakens them as well which will create pin holes and separation at the base of the paper folds.
Might depend on how much air pressure you are using ...
The single element filter is a very fine filter and should be thrown out and replaced every ten ours if you do not have an oil bath precleaner.
Jeez .... what's your day job ..... parts manager for dealership ? .... or sales rep for a filter manufacturer ?
Internal combustion engine air filters can often go far, far longer than what is commonly believed (as a consequence of air filter manufacturer propaganda) - although in the case of tractors, which often operate in much dirtier environments - that's much less the case than with other over-the-road vehicles - as an example:
I have an '06 Dodge Sprinter (Mercedes) that gets driven over the road .... it's a diesel engine and has a filter minder .....
I've changed the air filter exactly
twice since we bought it new ..... first time was at 123,000 miles ...... and the second time was at 271,000 miles .... neither time was the filter minder indicating a restriction and the vehicle was running fine (no loss of performance) .... the vehicle now 282,000+ miles on it.
Having said that, I do agree that equipment that operates in a "severe service" environment does need more care and maintenance than others do ....