Have you tried your local Cat dealer?
Yes, I've called multiple times but ended up getting mostly dead ends. Only the parts department person was able to tell me they sold kits but wasn't able to tell me if I can mail them in myself or if I have to make a trip back to them for drop off. The Austin branch dealer sends them to San Antonio (same overall dealership) where the lab is located so still very local. I agree sending oil samples from a Cat product to a Cat oil lab will yield best results.
6-8 samples a year seems awful low when all the systems are considered. 2-3 samples on the engine, 1-2 on the coolant & hydraulic system, and at least one each on the swing drive and final drives. That’s 10 for a start without even considering your other equipment.
I agree there is a higher initial start up volume for sampling when you have to do everything at once. I was thinking more of the steady state where I put 150-250hrs a year on the machine and keep tabs on the injectors, rings, bearings, etc. That's about one engine oil a year and other oils and coolant every other year. The excavator runs great- only white smokes some on cold morning start up for a few seconds after it's been sitting a while so I might have to play with a bad injector but oil sampling should better guide me. Doesn't smoke at all if started within a week or two of last shutdown so I'm not too concerned. I've only used a half-tank of fuel since it was delivered so just getting used to it... but would like to start an analysis program before getting busy with it.
Since the machine has ~8k hours but I don't have any history of the oils/coolant, I can easily take initial samples with current oils but not sure if they will be useful (at least not on the engine for sure and maybe not the hydraulic system). The final and swings I assume could be useful but even then, I have no idea of the type of oil used, hours on it, etc. I believe the machine was serviced by Cat in the past so what are the chances Cat would be able to use the previous sample data (if it exists)?
In my experience the Cat labs will interpret samples from their own brand of machines. One must take any interpretation they make of other brands as an opinion based on general knowledge. Their big advantage is that the labs are usually somewhat local and you can have results usually in less that three days from delivery to the lab. Other outfits require a mailing out of state and you are lucky to get a result in less than two weeks.
The speed of the test is not too much of a concern. I don't use my machines to make money, I only work my own personal land, so I'd be more concerned with getting the right lab to do the right tests. As mentioned, Cat is the right choice for Cat products. I don't know if they can do as useful interpretations on a couple older Cummins NHC-250's engines or my older JD tractor. For the Cummins I'm really interested in tracking the usual fuel dilution, antifreeze contamination, and high metallics in the engine oils. I don't know what is the best place to go for Cummins specific data since these engines faded out in the 80's.