Posted by Traveler on April 16, 01 at 13:56:30:
I couldn't find a reference to copy and post but I can tell you what I've read and what I think it does.
It is a software program that keeps track of engine usage and essentialy "counts RPM's". I think it weights use under severe conditions heavier so if the motor is opearted at high manifold pressure (towing) or makes a bunch of short trips (warmup) it will time out sooner. I doubt there is any real sensor in the oil, and it would be based on the oil recommended in the owner's manual (dino).
Under these assumptions, it is not useful in determining the life of synthetic oil. The best thing to do is choose a change interval, 6K or 7.5K miles, etc., and send a sample out to Blackstone Labs. The results will tell you how much degredation has taken place and also whether there are unusual wear metals in the oil.
Have used both M1 and AMSOIL and use M1 currently. AMSOIL requires a new filter and an oil top-off at 12.5K if you are shooting for the 25K service life. I choose to dump it and put in new, so I'm using M1 5W-30 that we occasionally find at Wal Mart for $ 14.99 for a 5 qt bottle. I have run the M1 for 10K intervals in my SSEi with no ill effects and it is still only a half qt low and brown but transparent after 10K. Ran my 454 Sub to 6750 miles on M1 5W-30 and the blackstone report didn't show any signs of breakdown.