Why no Na in diesel oils?

Status
Not open for further replies.
Joined
Jan 29, 2006
Messages
2,435
Location
Mizzou-land
In addition to Zn/P, it seem that PCMOs use either Mo/B additives OR Na additives. On the other hand, based on the PQIA data, the diesel oils don't seem to use a sodium based package. What gives? Is there a reason for this difference?
 
Hopefully, one of our experts chimes in. However, if this were a quiz show question and I were pressed to answer, I'd venture a guess that the magnesium based detergents are a better fit for getting the high TBN and low SA required by certain ACEA specs that the big name HDEOs meet. I would gather that having a TBN of 10 or higher along with SA of <=1 isn't easy, and then there is one ACEA HDEO spec that some meet that calls for low phosphorous, too, in addition to high TBN and low SA.
 
Maybe I should have asked the question a little differently. I am trying to figure out why VOAs show that the vast majority of PCMO have either Mo and B OR they have Na. On the other hand, we do not see the absence of Mo and B in the diesel oils. Why not? Why can PCMOs be formulated without Mo/B as long as Na is present, but we don't see the same trend in diesel oils? I don't see the connection between the absence of Mo/B and TBN.
 
Well, that's a good question; hopefully someone with the knowledge will see it. There certainly are some diesel oils without measurable amounts of moly, and there have been Na additive package oils with moly in the past. It's just that some have gotten rid of the moly or haven't historically used it. As for TBN, that point mainly dealt with the issue of magnesium detergents versus calcium in ACEA E7/E9 type lubricants.
 
There may be technical reasons that I couldn't give but I have a guess. My thinking is that maybe it has to do with not complicating oil analysis in diesel oil. (?)

Typically, diesel powered vehicles accumulate miles much faster and end up with many miles in short order. With such a large investment it pays to watch for developing problems such as coolant contamination. Even with oil analysis trending, I think the sodium additive would complicate things.

Obviously car engines have coolant in their veins but typically see far less miles accumulated and those miles are far less stressing compared to a hard worked diesel.

Sodium is a multi-tasking additive like calcium and leaves a less tenacious ash than magnesium therefore beneficial in exhaust aftertreatment (dpf). So I think it may be left out to prevent more complication in oil analysis.

Am I being too simplistic here?
 
aside from whats mentioned above...

MAYBE lower (overall) revs= less need for si based anti-foam additives?

just my 2C
 
Status
Not open for further replies.
Back
Top