31C707? Buy a straight 30w Synthetic- I think Royal Purple has one to see if that may make a difference. It may be that you have the start of a head gasket leak.

I checked my compression today and it read 105psi. I am not sure what the factory spec is, but it seems like a reasonably good number for ignition.

I am wondering if burning oil simply gunks up spark plugs and perhaps I may need to change them more often. Another thought I had was that this new syn.oil I put in this season is removing the old sludge from the conventional oil of other seasons, and it is ending up on my spark plug.

Other than burning oil and gunking up the spark plug (the plug never fouled by the way) the machine seems to run fine. I am just concerned that something else might be wrong, causing bigger problems. It was a pretty gunked up plug for one season's use.

If anyone else has some thoughts or some test I can run or something I should check, I would appreciate the suggestions.

I'd say either the engine just started burning oil or your synthetic oil is no good. I'd switch oil in a hurry and then make comparisons. Briggs and Stratton 5w-30 Synthetic Oil is made for hotter running air cooled engines. Briggs Synthetic Oil is their oil of choice in all their engines at all temperatures. It's available at Tractor Supply Company and other places as well. Link to Tractor Supply's display of Briggs oil below.

Here is a link that might be useful: Tractor Supply Briggs Synthetic Oil

Point 1 never never add any crap in the gas or oil. Point 2 make sure your air fliter is clean and your carb is not running to rich. Crud on a carb is always a sign of a poorly set-up carb or a worn-out engine. Note there is never a fix in a Can. Stick to regular gas and a good name brand 10w-30w oil and that engine should last at least 30 years.

I remember when synthetic oils first came out, and it
was recommended to be used in new engines only and never
use it in an old engine that was use to petroleum
based oil. I never learned what the real reason was,but 'word on the street' was that it would loosen up the crud that was built up by the petroleum oil.
However, I don't see how that crud could get into
the combustion chamber and foul a plug.
On a different note, I once had a 1960 Ford Falcon
that had one plug that would foul up, as optsyeagle
describes his plug to be. The cause was the valve
seals for that cylinder.

"Point 2 make sure your air fliter is clean and your carb is not running to rich."

How would I determine if my carb is running too rich?

A fast way to determine if your carb is running rich, 1 repalce spark plug with new and remove or replace your air filter with a new. Now start you engine and run it for at least 5 minutes. Remove your plug and it should look like new or close to if it is black then you have a very rich running carb. Note if your engine is worn out or burning oil you will see smoke and a bad exhaust smell. Never never add anything to your gas or oil No shuch thing as a fit in a can.

rolm, Briggs and Stratton recommends against using 10w 30 conventional oil above 40 degrees F because of increased oil consumption in air cooled engines. If using a multi-grade oil use a synthetic.