The gray paste is usually powered aluminum mixed with oil.  The powered aluminum is ground up piston skirt from sand, dust or any abrasive that makes it way into the engine. 

As I thought, going to try a K&N cotton element oiled this weekend. 

The most common path into the engine is through an improperly serviced air filter.

Yes, I wonder if it's lack of cleaning or it just passes sand.  This is with 16-18 hours run time.


Here's the new set up, I'll report back how it does