I have a non-scientific analysis I do when changing the oil.  I always look for metal flakes in the oil.  Now these are mostly captured by the filter in units with a filter but push mowers and such without a filter show less of this metal flake when using a synthetic vs. conventional oil.  That alone tells me that the synthetic is doing something better than conventional.
I always notice that changing the oil in a NEW engine right after you mow with it one time gives you a TON of metal flake from the engine breaking in. I usually run conventional for a mowing, change the oil, run it 3-5 mowings again on conventional, then switch to syn.
	
		
			
		
		
	
			
			I always notice that changing the oil in a NEW engine right after you mow with it one time gives you a TON of metal flake from the engine breaking in. I usually run conventional for a mowing, change the oil, run it 3-5 mowings again on conventional, then switch to syn.
 
				