This is not Fernandez it's one of his buddies from work

It may not be as accurate as an oil analysis but at the same time if you get enough engines together and do enough testing you can get a general "slope" I guess you could say of how the oil breaks down over time at a given engine speed, load, temperature, ect,ect. and be able to program your system based off that information.

My Saturn has an oil life monitor developed by GM. It doesn't use a sensor but uses various factors (engine speed, temperature, ect, ect) during the operation of the engine to determine proper change time. That system is based on using a Synthetic 5W-30 oil so if you use something not within the GM Spec 4718M (which is like 7 diffrent syn oils) there's no way to know if they system will tell you to change at the proper time.

A lot of engineering and work went into the system and I trust that the guys with engineering degrees know more about this subject than I do. I simply spin my own wrenches not design, engineer, build, and refine engines for mass produced automobiles.

I routinley go between 7 and 8 k miles on an oil change. I have a few oil samples sitting out waiting to go to Blackstone labs but still haven't gotten them out yet.

If you're interested you can go to this link
http://www.redlineforums.com/forums/...il-life-7.html
It's a link to a page on the discussion of the oil life system on the Saturn. The first post on that page is probalby the most informative. We don't use the exact same system but it gives you an idea of the amount of engineering that goes into these systems.