I just found a heap of info on the net ... and copy and pasted it .... hee hee

Google is your friend.

There's a guy in www.fordforums.com.au that has been doing a regular oil analysis on his Territory and has been posting the details everytime he does an oil change .... his old oil gets sent to a laba nd they send his the results of what his oil is like.

Interesting read indeed of what happens to the oil as it slowly breaks down over time in a petrol engine.

is there any problems with using castrol magnatec in a 1993 4.0L????????
if i remember right its like a 10/40
or something liek that

Don't know if it was in the posts earlier by Mechan1k, but SAE = Society of American Engineers (99% sure I remember correctly).
It's pretty much just a classification society that nominates grades for different viscosity oils. Also Viscosity isn't the resistance to pouring, it's the resistance to flow, and the more viscous or resistant to flowing the oil is, the higher the number.
The common grade oils for Falcon's such as SAE 20W-50 mean that it has a viscosity rating of 20W (less viscous) when cold (W = winter) and 50 when the oil is hot and working.

Oil itself doesn't really break down so much as the detergents in it break down scum build-up and the oil gets contaminated, but it's pretty much the same thing. Not doing a point-and-laugh haha-you're-wrong thing, just a few slight corrections to increase the accuracy of the technical documents