At what point does Calcium inhibit Zddp?

[FCD]

So I've read several times here that Calcium can in essence inhibit Zddp in an engine oil from really working properly, effectively making the oil behave like an oil that had less Zddp than it actually has.

I just randomly the other day stumbled upon a Uoa of an oil that i've used in the past and recommended to friends etc which is Shell Rimula R4X 15w40 , it's a A API SL , E7, CI-4 old school HDEO, and i didn't know it had 4000ppm of CA , plenty of ZDDP for sure, but it got me thinking, with so much CA how does this oil really behave? Like one with 900ppm would? Thoughts?

Also i was surprised by 500ppm of Boron, i don't think i've ever seen that much.

 

[buster]

When you buy an oil that meets xyz spec, it's already been formulated, balanced and tested. There would be no way for a consumer to know at what point Ca inhibits ZDP. This is why I don't like adding aftermarket additives to a fully formulated product.

 

[Cujet]

Low viscosity and low ZDDP has always been tough on cam lobes and the associated parts. While I've never done or even seen cam lobe testing of oils with low calcium, I've used race oils in turbocharged road race cars for decades. Know that many race oils are low in Ca and do not seem to provide additional cam or lifter protection. In fact, for the most part, we found that the classic high calcium M1, 15W-50 and the V-Twin 20W-50 were superb oils for our tortured engines.

 

[Jetronic]

So I've read several times here that Calcium can in essence inhibit Zddp in an engine oil from really working properly, effectively making the oil behave like an oil that had less Zddp than it actually has.

I just randomly the other day stumbled upon a Uoa of an oil that i've used in the past and recommended to friends etc which is Shell Rimula R4X 15w40 , it's a A API SL , E7, CI-4 old school HDEO, and i didn't know it had 4000ppm of CA , plenty of ZDDP for sure, but it got me thinking, with so much CA how does this oil really behave? Like one with 900ppm would? Thoughts?

Also i was surprised by 500ppm of Boron, i don't think i've ever seen that much.

View attachment 215127

The boron is likely part of the calcium detergent/dispersant package, so goes up with higher calcium content boron end capped dispersants

 

[Jetronic]

Low viscosity and low ZDDP has always been tough on cam lobes and the associated parts. While I've never done or even seen cam lobe testing of oils with low calcium, I've used race oils in turbocharged road race cars for decades. Know that many race oils are low in Ca and do not seem to provide additional cam or lifter protection. In fact, for the most part, we found that the classic high calcium M1, 15W-50 and the V-Twin 20W-50 were superb oils for our tortured engines.

calcium des act as a friction modifier, and can have EP properties. It's the reason we don't really see oils abandoning calcium completely.

 

[weasley]

There is a lot more to it than simple Ca and Zn ratios. It depends on what form each element is in. What type of ZDDP (there are lots, each with different properties), what type of detergent (ditto), what other chemicals are present and so on.

Many of the molecules in an oil are in some way "surface active", meaning they interact with metal surfaces in greater or lesser ways. This sets up a competition between molecules for the surface (I like to imagine lots of hungry piglets fighting to suckle) and those with more affinity for the surface can win, but these affinities will change dependent on the details: surface metallurgy, contact pressure, temperature, contamination and so on.