http://www.carbibles.com/engineoil_bible.html

A great read!, it certianly solved the mystery of why the engine was pitch black when I removed my tappet cover off of my XF '86 Wagon..

I would say a lack of maintenace from my parents caused this. (Car is a donor)

I would recommend using caution when using engine oil cleaner additive, eg don't run it on the road, that website though recommends high RPM's, what do you guys think?

In a few days I'm gonna do the second 'cleansing' on my engine and then replace the oil and oil filter afterwoods..again.

Cheers!

Note, I don't have any affiliation with the above formentioned website or its author, I'm just a concerned Ford owner.