What I do to collect is simply drive the car for a while, to get it up to temperature. Somewhere in the instructions they suggest 500 miles to get everything mixed up, but these kits are usually designed for the trucking industry. Once the engine / oil is hot, I go right ahead and drain the oil for a change. I let it flow for a couple of seconds, and then stick the collection bottle right into the stream of oil flowing out into the collection pan (Cleanliness is key). I fill the whole bottle which is maybe a few ounces, ten let the rest drain out and perform an oil change as usual.
I use wearcheck USA (
http://www.wearcheckusa.com/ ), which seems to have the best prices around ($12 for the simple kit, $16 for extra testing). I use the simple kit, which just looks at wear numbers, not toal base or total acid number (useful if youre extending drains). I figure I can see the ppm of aditives, and can see the wear metals. this is good enough, because diesel rated oils have a very robust additive package, and surely can go for much longer than my intervals. If not, Id think the additive amounts would be off. The key is to not change brands too often, because additive clash will reduce the TBN much faster than any acid/soot fighting done by the oil will.
My analysis was good, and a member on the mbz.org list said that with soot at 0.9, the oil was totally fine and I could have left it in longer. Right now I have dino delvac in there, but I am thinking of using synthetic delvac (I have a feeling my MPGs were better with it than the current 15w-40 delvac 1300s dino oil) permanently, because if I do two drains of dino oil per one of delvac, Im looking at about $40 for dino and filter vs. about $47 for the synthetic and filter, but it saves me time rolling around under my car (which Ill do anyhow), black sooty oil all in my skin and on my fingernails, and probably 1-2 MPG better, from what Im seeing.
Hope this helps,
JMH