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Originally Posted by Pharmacist
actually it's the vvel. The swinging lever arms on top of the valves that go back and forth generate a lot of friction and heat. That's why the vq37 generates proportionately more heat than many other engines, and that's part of the reason why nissan uses diamond like coating and nano particles in ester oil, to try and reduce the friction.
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Not actually true...Nanoparticles don't even play a role here, chemistry and some physics; it's chemical compatibility between the coating and an additive in the oil. Nissan's engineers and tribologists who worked on their Hydrogen free DLC coating used in the VQ37 and its relationship with the "ester oil" published their research. I do not have the rights to redistribute specifically what their findings were, but they have been widely recognized for their success reducing valvetrain friction. In fact, they were able to achieve friction levels in the "superlow" regime (coefficient of friction <0.01) at the boundary condition...on par with the rolling contact friction level of needle roller bearings.
This is of course, assuming the engine is being run with the recommended ester oil. Other oils can (and do) still perform well in this engine, but the "magic" doesn't happen unless the specially matched oil is used. Use whatever oil you want, you won't be harming your engine either way, but it was designed to use the ester oil (which in turn was designed by Nissan to be used specifically in engines using a H-Free DLC...yes, they did actually engineer this oil blend, can't say who manufactures it). The benefits of the ester oil aren't necessarily capturable in the traditional UOA, and it's also not a super-long service life blend either so it's not surprising to be at all that the oil doesn't perform spectacularly in UOA. The nerd in me says to use the ester oil, but change it more frequently you would your typical high-performance synthetic.
There's countless threads here and elsewhere filled with misinformation about how their ester oil and VVEL work (or don't work), as someone who has thoroughly read (and has the education to understand) their research (before I even bought a 370Z), what Nissan's accomplished is quite impressive on a scientific level, let alone commercializing the technology and applying it to production internal combustion engine.
Ok, end rant...sorry for getting off topic, back to the oil cooler!