I've read several notes over the months that indicate that most oil-analysis labs will calculate a Total Base Number only for extra cost. I seem to remember in one case that extra cost was around the price of the basic analysis! I bought a 6-pack of analyses from OilGuard/MTM when I bought my yet-to-be-connected bypass filter. (The 6-pack was only $54 or $9 each!) I called yesterday to see if they could/would calculate a TBN; the fellow said they include a TBN calculation for all oil samples from diesel engines and would I like that done? I said yes. We'll see in a week or so, but apparently all you have to do is ask...and for only $9! BTW, I submitted my 2nd sample of M1 0W-40 (this time with only 2400 miles on it) and a sample of virgin Red Line 5W-40.