Originally Posted by 911medic
I think that analysis would certainly be definitive, but I'm not sure you're going to find someone willing to spend the time and money to collect and send the samples into someplace like Blackstone Labs to get it done. And I'm not sure what kind of sample quantity they require, so you may have problems getting adequate sample volume from the valves themselves. And lastly, I'm not sure that you wouldn't change the chemical content during the burning/coking process on the valves, which may make it impossible (or much more expensive) to match a source to the end product.
Your analysis is correct.
In retrospect I think a simpler (and less accurate) test would be to take a small amount of the wet valve area buildup and compare it with a similar small amount of oil from the catch can. A color analysis of the two samples might answer the question IF there is a noticeable difference.