Calcium vs. Magnesium sulfonates in engine oil?

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I was looking over the PQIA report on Synthetic 5w-30 motor oils and the percentage of magnesium used was the highest w/ Castrol Edge (1462) and Mobil 1 (772). The rest used calcium mainly in their additive pack. What I have read on magnesium on PQIA is that: (1) more expensive the calcium, (2) improved rust production (rust inhibitor?). The reason that I'm asking is that my VW Golf 2.5L has an iron block engine. Could this be a significient reason to use Castrol oil? Presently using GC 0w-30 which IMO is an exc. oil for this engine. Looking over Castrol TDS report on their website (which is very dated-2002 Rev 1), no info could be found on the 0w-40 oil and 0w-30 oil had .35% calcium % weight reported. (no magnesium % reported at all?) Honestly, I believe I'll only used Castrol's 0w-30/40's oils exclusively in this car for as long as I own. I wonder what Castrol's 0w-30 & 0w-40 add pack is? (Is it high on magnesium as the 5w-30?) Mostly calcium is used in all motor oil add packs that I've seen. I'd be interested in your thoughts. Thanks, Bill.
 
I note that Castrol motorcycle blend uses much higher Mag than several others I've tested, and less Cal. Not sure this has anything to do with your needs, but thought it interesting.
 
Originally Posted By: sparky123
I was looking over the PQIA report on Synthetic 5w-30 motor oils and the percentage of magnesium used was the highest w/ Castrol Edge (1462) and Mobil 1 (772). The rest used calcium mainly in their additive pack. What I have read on magnesium on PQIA is that: (1) more expensive the calcium, (2) improved rust production (rust inhibitor?). The reason that I'm asking is that my VW Golf 2.5L has an iron block engine. Could this be a significient reason to use Castrol oil? Presently using GC 0w-30 which IMO is an exc. oil for this engine. Looking over Castrol TDS report on their website (which is very dated-2002 Rev 1), no info could be found on the 0w-40 oil and 0w-30 oil had .35% calcium % weight reported. (no magnesium % reported at all?) Honestly, I believe I'll only used Castrol's 0w-30/40's oils exclusively in this car for as long as I own. I wonder what Castrol's 0w-30 & 0w-40 add pack is? (Is it high on magnesium as the 5w-30?) Mostly calcium is used in all motor oil add packs that I've seen. I'd be interested in your thoughts. Thanks, Bill.

Magnesium has some advantages over calcium as an additive in oils used for diesels.

You might see if you can find "Preventing Catastrophic Valve Failures In Detroit Diesel 149 Engines With Chevron RPM Motor Oil" by J. A. Mc Geehan, W. Alexander, P. R. Ryason, and B. L. Schmidt.:

"Magnesium containing components of the valve seat deposit are unstable, decompose, and do not remain on the valve seat. Thus, the valve seat deposit is thinner with this specific magnesium-calcium detergent oil. A thinner deposit on the seat results in a lower valve seat temperature because there is less insulation between the valve seat and the cylinder head. As previously described, the thinner deposit prevents localized loss and channeling of the deposit, and subsequent valve failure."

Magnesium Sulfonate Additives
 
Originally Posted By: gregk24
I thought Magnesium was a sign of cheapening?


No you generally see it show up in higher level offerings.
 
Originally Posted By: KCJeep
Originally Posted By: gregk24
I thought Magnesium was a sign of cheapening?


No you generally see it show up in higher level offerings.


Oh ok, then Castrol has been on point for a while now
wink.gif
 
Hi,
Wilhelm_D - The 149 Series DD engines were two strokes!

They had very specific lubricant needs - API CF2, monograde viscosity 40 and 50 (application specific - SAE30 and multigrade lubricants specifically prohibited),SA 0.8%, an Fe max condemnation point of of 35ppm. Only fuels of less than 0.5% sulphur were permitted

DD two stroke diesel engines were/are special "animals" with very special maintenance requirements
 
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