Small Engines (Lawn Mowers, etc.): Oil Burner, sae 30, valve seals

Question
I have a lawn tractor which is powered by a B&S 18.5hp, Intek engine, 31P7770299E1, which is burning oil yet has good compression (135 to 150 psi). It starts and runs fine other than it is using oil -I have to add a small amount of 5W-30 to keep it above Min after every use. I suspect valve guide seals. Do you agree? If so, I'd like to know if there is any test I can do to confirm this before teardown. If I have to teardown is there anything I should lookout for and what would you advise for valve clearance settings.

Answer
Are you using the mower to plow snow?  If not, switch to SAE-30 to reduce oil burning.  As for testing, Briggs sells a leak down tester to check the compression and valves.  The leak down test will usually identify work valve seals.

Try the oil first.  I'd recommend changing the oil several times after switching the SAE-30.  I'd change the oil 3-4 times to clean out all the old oil and dirt inside the engine.  

Let me know what happens after switching oil.
Eric