To increase engine life a super clean airfilter is a must.
Here is one of the things that to do to make sure no dirt gets into your engine.
Step 1: grease the filter
After oiling yout airfilter, spread a thin layer of grease on both ends, as shown.
Step 2: slide it on
Carefully sliding it onto the filter body.
Step 3: tuck it in
After scewing the top on, carefully tuck the airfilter into place.
The grease makes an airtight seal so that no dirt can get around the foam filter.
Then apply the outer filter.
source: tytessmann.com