Magnesium in oil?

Not open for further replies.


Staff member
May 27, 2002
Guelph, Ontario
I was just looking over the oil analysis spreadsheet, and on the virgin oil samples I noticed that Castrol Syntec contains 571ppm of magesium while the GTX contains zero. What does the magnesium do exactly and what advantages does that give Syntec over GTX? I had always assumed that Syntec and GTX had the same additive package, with just a different base oil, but I guess I was wrong. (write this down on your calendars it doesn't happen too often)

From experience I know magnesium is a very soft metal, so perhaps they use it not as a FM, but more as a sheer protection metallic like how Zinc is often used. It would be much better for the rings to slide on a cushion of zinc or magnesium on a cold start or under high load than to grind into the cyl wall
. Thats my guess - but I might be wrong
Calcium and Magnesium are elements used in metallic (ash-type) detergents and are often in the form of calcium and magnesium sulfonates.

If the calcium and magnesium is in the form of "phenates" then the additive is a multifunctional additive which:

1. provides detergency
2. is used to attack acids and keep the TBN at a decent level
3. acts as an oxidation inhibitor.
So in the case of these two oils, the Syntec would keep the engine cleaner and retain it's TBN longer then right?
Not necessarily. The GTX may contain a different additive package that accomplishes the same thing.

Here is what I think is happening. The Syntec needed an additive package to be more compatible with the Group III base or was developed just for the GIII dino oil.

The fully dino GTX GII base oil is using a different additive package.
Not open for further replies.