"KC" wrote in message
...
I use a riding mower/garden tractor in an extemely dusty environment.
The manual states to not blow out the air filter since it could damage
it.

Bullshit.

Yet at $17 per filter, changing it after each mowing is out of
the question.

You already know the answer to this question. The reason the manufacturer
doesn't want you to blow out the filter is that new ones are $17 a pop.
Same exact reason that inkjet printer manufacturers don't want you to refill
ink cartridges. You're gullible enough to believe that you shouldn't blow
out the air filter, just because it says not to in black and white in the
owner's manual.

So my question is that after careful blowing out the
filter from inside-to-outside, any guesses as to how many times I can
clean it before replacement?

Theoretically, one filter might last you long enough that the tractor will
retire or be sold/traded with the original filter in it. You've got to
understand the purpose of the filter, and then you will be able to use your
best judgement. The reason you don't want dust in the engine is that it
acts like sandpaper between the cylinder and cylinder wall, wearing down
these surfaces that need to be closely mated. This could cause performance
problems (in extreme dusty conditions). At best though, dust in the engine
will cause the engine to wear faster, lose compression, lose horsepower,
eventually it will be unusable/worn out.
So, keeping the dust out of the engine will help the engine last longer.

So how do you know if an air filter is still usable? Inspect it visually.
Can you see any holes that will allow dust to travel through the filter,
unimpeded? If not, then keep using it. If you're really paranoid, replace
it once a year or once every other year. If you're not paranoid, just blow
it out after every mowing, then carefully inspect it before reinstalling
t. -Dave