I found this on a 350Z site, linked to another thread, sorry if this is already out there, but in case it's not, here you go.........
For those who might find this stuff interesting, here is a post I made over in the 370Z forum in regard to the special Nissan ester oil:
I tried posting this over at my350z.com, but it would only post the first paragraph or two, even in a second post. So, hopefully you'll see this here. Sorry for somewhat OT guys, but maybe everyone will find this a bit interesting:
The valve clatter issue was present on the G37
as well, which also uses the VQ37VHR engine. The VQ37VHR uses Nissan's patented hydrogen-free DLC. What's being postulated is that an ester-based hydrocarbon is needed to quiet the valve train because of the H-free DLC found on the bucket face of these engines.
Where I get confused is looking at the VQ35HR, which also uses Nissan's patented H-free DLC coating on the bucket faces, but doesn't share the valve clatter complaint with the VQ37VHR. So why is the H-free DLC now the culprit for valve clatter?
Looking at the two engines, and the complaint singularly associated with just one of them, I find it hard to believe that the common DLC coating is the culprit rather than the unique VVEL mechanism found in the VQ37VHR. Further, I find it hard to believe that using an ester base oil is the solution, based simply on an ester's polar affinity, when there are a good number of other hydroxyl compounds used in engine oil with similar hydrophillic properties. This becomes especially curious when examining the patent for Nissan's ester oil, which is not an ester-based product, but does have a unique ingredient I have not seen in an oil formulation before.
Looking at Nissan's patent for this new oil, we can see the use of an ester additive. Quote:
"In the present invention, the content of the fatty acid ester-based ashless friction modifier is not particularlyrestricted, in which the content is preferably 0.05 to 3.0 %, more preferably 0.1 to 2.0 % and most preferably 0.5 to 1.4%, based on the total amount of the lubricating oil composition."
Ester additives are often favored for their natural polar affinity, but also for their solvency, high viscosity index, and high-temperature/high-shear stability. They also react with water and are therefore hydrolytically unstable, a natural drawback to their hydroxyl construction
. Thus, the use of ester is required to be minimized to a proportion beneficial for its solvency, rather than its lubricity. Quote:
"If the above [ester] content is less than 0.05 %, a friction lowering effect tends to become less. If the content exceeds 3.0 %, the friction lowering effect is excellent; however, the solubility of the ashless friction modifier to the lubricating oil and a storage stability of the ashless friction modifier are remarkably deteriorated so that a precipitate tends to be readily formed, which is not preferable."
Also, just to be clear, most ester additives are not the same as the diester and polyolester (POE) base oils used in oils like Motul or Redline. Fatty-acid ester additives are often variants of trimethylol propane C8/C10, known as TMP esters. The base oil used by Nissan in its testing of this new formulation was actually a polyalphaolefin, or PAO. The oil can be synthetic or conventional based, however. Quote:
"In the present invention, a mineral oil or a synthetic oil may be used as the base oil, in which the base oil is preferably a main component of the nanoparticle-containing lubricating oil composition. The "main component" means a component occupying not less than 50 % based on the whole amount of the lubricating oil composition."
The key for the base oil is that it not exceed 15% aromatic content, so that oxidative stability is maintained. PAO has excellent oxidation resistance due to its fully-saturated nature. Fully-saturated hydrocarbons like PAO are also very thermolytically stable for this reason, and for the same reason, are very poor solvents. The use of a conventional base oil with a fatty-acid ester additive is described as a potential alternative when a solvent-refined conventional oil additive is also included. Quote:
"Additionally, in case of using a highly hydrocracked mineral oil,1-decene oligomer hydride or the like as the base oil, the composition high in friction lowering effect can be obtained even if the total aromatic content of the base oil is not more than 2 % or 0 %.
For example, in case that the content of a fatty acid ester-based ashless friction modifier in the base oil exceeds 1.4 %, the base oil may be inferior in storage stability, and therefore it is preferable to mix a solvent-refined mineral oil, alkyl benzene or the like into the base oil as occasion demands so as to regulate the total aromatic content of the base oil to, for example, not less than 2 %."
Now, whether PAO or conventional based, the whole point of the paper has been centered around the use of several solvent and carrier additive possibilities such as TMP esters which can adequately suspend and diffuse a nanoparticle lubricant. Nanoparticles such as organomolybdenum compounds have been in use for many years as an engine oil aditive. The most common are molybdenum dithiocarbamate (MoDTC) and molybdenum dithiophosphate (MoDTP). Zinc dithiophosphate (ZDDP) is also very well known, although there have been inconclusive studies to suggest phosphorus is detrimental to modern catalytic converter life expectancy, and so it's use is declining. In addition, low SAPS oil restricts ZDDP and Molybdenum Disulfide use in order to reduce ash. AntimonyDTC is another common, albeit expensive, nanoparticle. Nissan's patent addresses a nanoparticle which is ashless, durable, presents no issue to modern catalysts, and exhibits a low friction coefficient- diamonds, or rough chemical equivalents at least. Quote:
"Additionally, it is preferable that all or a part of the nanoparticle is formed of a carbon material whose main component is carbon.
Examples of such a carbon material are soot (and carbon black as an aggregated body of soot), DLC (diamond-like carbon), diamond, and the like. Such carbon materials may be suitably mixed. Additionally, the hydrogen content of DLC is preferably as low as possible, and specifically not more than 10 atomic % and more preferably not more than 5 atomic %, and further more preferably not more than 1 atomic %."
H-free DLC is a potential nanoparticle base, and guess who owns the patent on the world's first hydrogen-free diamond like compound? Nissan. I think Nissan has figured out how to make their H-free DLC into an additive which needs a good solvent to help adhere it to surfaces. Quote:
"In case that the nanoparticle formed of diamond is of single crystal, amorphous carbon (existing at grain boundary of a polycrystalline body or an aggregated body) does not exist in a surface layer, and therefore the additive having hydroxyl group tends to be further readily adsorbed to the nanoparticle under the action of dangling bond in a surface layer of sp3 structure."
Ester base oils and ester additives are nothing new and not special. They have drawbacks of their own when used as engine oils. H-free DLC is new, is worth a couple of patents, and is expensive. I think this is what we are getting with Nissan's "special" ester oil.
Consider the overall mechanism of the VVEL system, and it becomes clear that while it is a good bit simpler than BMW's Valvetronic design, it is still a rather complex system with unique lubrication needs. The HR uses DLC buckets without the valve clatter, so why would the DLC buckets be the issue on the VHR engines only? The VVEL system, however, is unique to the VHR and would no doubt require special lubrication needs in order to maintain the design specifications. Even BMW's systems don't rev to 7500 rpm and have the overall lift offered by VVEL. This is a well-engineered valvetrain with, arguably, extreme forces present when one considers the amount and array of reciprocating and oscillating masses involved. It makes sense that Nissan would desire a special surface additive to extend the life of this mechanism when other oils may fail to protect these surfaces as the lubricant overheats and moves from elastohydrodynamic lubrication to boundary lubrication. This nanoparticle additive would potentially offer the surface protection needed under such duress.
Just my thoughts.