Just thought I'd share my Blackstone oil analysis results that I've accumulated after 2 reports since I purchased the car 2 years ago at 45,000 miles and am now at ~65,000 miles.
When I bought the car I was doing oil changes every 3,000 miles. I submitted a test sample to Blackstone and it was concluded that I could try stretching my OCI to 5,000 miles.
After doing a 5,000 OCI (about 5 months of driving for me), I sent in another sample and I've been okay to go to a 7,000 OCI based on the test results.
For me, this equates to maybe doing one oil change per year
I primarily do around town driving with 3-4 longer highway trips per month.
I bought a dozen filters at a bulk cost and the oil costs me about $30 at Wal-Mart depending on the sale.
As a result of doing this testing, I cut the amount of time, cost and waste down. Granted, the tests were about the cost of a full oil change, but with the results, I can be confident of my engine and oil condition. I probably won't need to check this again for another 2 years or so barring any other issues.
Theoretically, if I switched to Amsoil products that do have a higher TBN, I might be able to get an even longer OCI. However, Amsoil is considerably more expensive than the Pennzoil Platinum Synthetic. I haven't done a theoretical cost analysis, but at this rate, it might not be worth the trouble.
Anyhow, I think the Blackstone testing is worthwhile so as to check the condition of your engine, trans, and other lubricated assemblies. This also allows you to confidently asses and maximize the value of the lubricants.