Interesting that this came up today. I just got my report back from Blackstone this week. I went with BS since the pervious owner had some reports from them and they would just add on and make it easy for me to see the trend side by side. I am actually considering for my next oil change I will submit samples to both Avlabs and Blackstone just for comparison of the 2 labs, the data, similarity and most import to me the commentary around what was found.
I have a low time (Hobbs) but older engine (500 hours SMOH in 1990). For me trends and commentary on what is found is VERY important. I want to get the most of the engine and not pull the trigger on an OH out of fear, but rather from the data saying it's time. So far BS has been great, they are happy to get on a call and talk about the findings as well as hear what the owner has found during anything they have suggested. For example, change before this one I had high Chrome which suggests ring wear, unless you have Chrome cylinders. BS suggested compression and borescope be preformed. I did both, logged results, went through my logs and found that Chrome cylinders were used in the OH. Called them and we talked about the results they found after adjustment for Chrome cylinders, I gave them the results of the compression check (which was good) and what was seen on the borescope. They suggested nothing pointed to anything major and we would monitor the next sample to see the trend. Well this last sample came back with back to normal chrome content, YAY! but I do have some elevated tin, nothing crazy, just something to monitor the next sample.