Originally Posted by drisko
If you use anything other than the Nissan Ester Oil, you will most likely see a decrease in fuel economy and power output due to increased friction in the valvetrain. The only real benefits of a different synthetic oil, such as Amsoil or Mobil 1, are that they flow better in very cold temperatures (such as during engine start up).
I found an article on this issue. Here is an excerpt of some of the text:
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One of the main issues is that the Nissan 370Z and Infiniti G37 with the VQ37VHR engine experiences high oil temperatures. The high engine oil temps can cause the engines ECU to put it into a limp home mode where the engine rpm is limited, first to around 6000 rpm and if you don’t start to behave, a lower limit of about 3500 rpm is engaged until the oil temperatures drop below around 280 degrees and the key is cycled. The VQ37VHR is very prone to suffer from high engine oil temps during any sort of extended high speed driving such as motorsports events, and even non competition events such as track days and Autocrosses. The engine can also suffer from high oil temps even with short burst of full throttle use such as on an engine dyno, drag racing and even bumper to bumper traffic.
To understand limp mode we must understand what it’s protecting in the engine. The most oil temperature susceptible parts are the engines crank and rod bearings. The engines bearings are made of soft metals, such as aluminum, tin and zinc with other trace alloying agents such as indium which refines the metals grain for better mechanical properties. The reason why soft metals are used is that they offer good embedability. If hard contaminates are present in the engines oil such as casting sand, metallic particles, hard carbon bits and dirt, a soft bearing surface will allow the particles to become embedded into the surface of the bearing where the damage to the bearing and crankshaft can be limited. The contaminating particle will be soaked up by the soft bearing instead of being ground into the hard steel journal surface of the crank with damaging effect.
Soft metals can be used as engine bearings because under normal conditions, the crankshafts journals never touch the bearings surface. Since the liquid oil layer is not compressible, the crank rides on a pressurized hydrodynamic film of oil a few thousands of an inch thick that is maintained on the bearings surface by the engines oil pump. The oil pump must maintain pressure (this varies for as low as 5 psi at hot idle to more than 60 psi at higher rpm) and continually replenish the oil because the oil leaks out at the edges of the bearing and is flung out by the centrifugal pumping action of the rotating rod journals. This circulation is necessary because the shearing action of the oil in the boundary layer between the rotating crank journal and the static bearing surface creates heat and this heat must be dissipated. Most of the heat is removed by the oil as it passes though the interface between the bearing and crank.
The bearings, although soft still have to bear a heavy load because the incompressible liquid oil film transfers the forces acting upon the engines reciprocating parts to the bearings, thus the bearings have to withstand thousands of pounds of force even though direct contact does not happen. The best engine bearing have high embedability with a high load bearing capacity.
Usually everything works fine until a couple of things happen. In the case of modern late model engines, the green movement is to blame for part of the problem. In the last few years, Nissan has worked hard to make their cars green and more recyclable. In an engine traditionally one of the most toxic areas was the bearings. A few years ago, many Nissan bearings were made of trimetal construction using layers of lead, zinc and tin alloys of different percentages. This tri metal construction has been a mainstay of heavy duty bearing construction and composition for decades. The old Nissan bearings were very strong, heat resistant and durable. It’s a little known secret that old L-Series Nissan bearings are so strong and durable that many race engine builders use them, adapting them to other engines. The Infiniti IRL engine used in Indy cars used off the shelf L-Series bearings for this reason.
Sometime in the last few years, in an effort to be greener, Nissan discontinued the use of lead in all engine bearings. We know of this through discussions of sources deep within Nissan which will have to remain unnamed. At this time the engineers at Nissan noticed that warranty claims for bearing failure in the RB26 GT-R engine, another Nissan engine noted for running high oil temps, spiked. Nissan launched an intensive study on the reasons of this bearing failure and discovered that the new environmentally friendly bearings started to loose their load bearing capacity at temperatures as low as 260 degrees. Although there was plenty of reserve strength for normal passenger cars, the turbo high output RB motor pushed many sets of bearings to the failure point. Although you think of lead as a very soft metal with a low melting point, it was still a major contributor to the bearings mechanical properties and resistance to heat.
So as the oil temperatures climb, the bearings soften and loose their load bearing capacity, if the temperature climbs past 300 degrees and the engine is being pushed hard the bearing material can start to flake and spall. This disrupts the hydrodynamic film allowing metal to metal contact, resulting in catastrophic failure of the bearings, the crank, rods and even the entire engine often within seconds. Oil also begins to deteriorate quickly at temperatures above 260 degrees. It starts to oxidize and thicken, loosing its lubricity while forming sludge and varnish. This further compounds the problem, generating more drag and heat in the bearing/crank interface area.
Why does the VQ37VHR have such high oil temperatures? We have several ideas. The VVEL/ CVTC variable cam timing system needs a lot of oil pressure and volume delivered to it to function correctly. Oil pressure must be able to move the rotor position inside the intake cam gear to advance and retard the cam. The VVEL system with its many pivots, links and sliding surfaces needs a lot of lube to be pumped to it to keep it lubricated. These devices must be moved quickly against the great frictional and spring tension forces generated by the rotating valvetrain.
Thus the VQ37VHR has a big high capacity oil pump. A big high pressure pump puts heat in the oil from the pumping action itself. A lot of oil is pumped up to the heads to operate the VVEL system and released to the area under the valve cover, probably faster than it can drain back into the pan. At high rpm, this means that there is much less oil in the pan and the oil remaining in the pan gets pumped through the engine many more times, gaining heat from the pump, valvetrain and bearings as its circulated.
As the oil pumped to the head drains back to the sump, much of it lands on the rapidly spinning crankshaft where it becomes part of the churning windage cloud of oil and air gaining more heat as it’s whipped into a fog of oil and air by the engines crank and rods. The big oil pump also bypasses a lot of oil at steady throttle and low speeds where the continually adjustable CVTC/VVEL valvetrain is more or less static. The oil in the pan is pumped through the pump where it get heated by the pump’s action and bypassed to the pan, where it is again rapidly circulated by the oil pump again and again picking up more and more heat. Thus the VQ37VHR becomes an oil temperature generating machine.
The conversations on oil temperature issues leads to Nissans recommendations for Genuine Nissan "ester" based oil and the super expensive oil service. Posts on forums indicate that some Nissan dealers are charging up to $300 for an oil change for the special oil that is mandatory for use on the 370Z. Is this oil expensive? Yes, does it have significant value? Yes, is it mandatory for your warranty or to insure long engine life? No. Is it important if you are the type of driver that wants the best for your engine in terms of fuel economy, life and performance? Yes. Is the "special" oil market hype intended to enrich Nissans coffers? It’s up to you to decide, we will attempt to explain whats going on with the oil so you can decide for yourself.
Nissans oil was developed in a push to greatly reduce friction in an engines valvetrain. The valve train is the second biggest contributor to the total amount of an engines mechanical friction, the piston rings being the biggest contributor. Usually on most engines the valvetrain produces 15-20% of the total friction of an engine. An engine with a complicated valvetrain like the VQ37VHR is probably on the high end of this figure. Nissans special oil and their newly developed hydrogen free DLC coating on cam followers reduces the amount of friction produced by the valve train by a huge amount This can make a considerable difference in fuel economy and power output.
What is Nissans special oil? The oil was developed to complement Nissans Hydrogen free DLC coating used on the cam followers in the QR25DE engine, the VQ35HR and the VQ37VHR engines. DLC stands for diamond like coating, which is an amorphous layer of carbon crystals with hard smooth properties much like diamond. Most of valve train friction is created by the interface between the cam follower and the cam lobe. DLC is very slippery stuff and Nissan uses it to reduce valvetrain friction to improve fuel economy, reduce emission and increase power.
Nissan figured that eliminating the hydrogen molecules in the DLC coating would make it an attractor of polar molecules like those found in hydroxyl compounds. A hydroxyl molecule is highly polar hydrocarbon molecule. The polarity makes it a good solvent so it mixes well with other fluids, like oil. Nissan chose ester hydroxyls, part of the alcohol family, probably because the properties of esters in motor oil are well understood as esters have been used as friction modifiers in motor oil for decades. Nissan chose an ester called PAO an ester often found as a friction modifier in oil. By adding PAO so it would be around 10-15% of the oil, when combined with the hydrogen free DLC coating, Nissan created oil that would be attracted to the cam follower on a molecular level.
In studying the various technical white papers and patents for Nissan’s super oil, we are not exactly sure of its exact composition in terms if its is considered a synthetic or not. Nissans patents and technical documentation are very broad when describing the make up of the super oil, probably to protect against patent infringement and to make it hard for a competitor to make the exact same stuff. We can ascertain that the technology is compatible to most known base oils, be they synthetic, mineral or a blend and we do know that esters are synthetic compounds so at least the oil is probably considered a semi synthetic at the least. The Nissan oils bottle lable says petroleum oil under contents, a bottle of Mobile One doesn’t say this. The Nissan oil smells like ester oil use in AC systems.
The next unusual thing about Nissans oil is its innovative use of nano technology. To help lubricate areas of extreme pressure and friction in the engine, the biggest of which is the interface between the cam lobe and cam follower, engine oils have traditional used what are called extreme pressure friction modifiers. These typically are compounds that have a slight molecular attraction to metal and usually have a slippery metallic element to them. These are compounds such as zinc diphosphate, molybdenum dithiophosphate and molybdenum dithiocarbamate. These friction modifiers work pretty well for preventing metal to metal contact in an engine but they have some issues. One is that they don’t burn completely when they get past the piston rings and valve guide seals and create ash; this can end up being a hard but sticky deposit in your engine’s combustion chamber and valves that can stick rings and valves, raise compression to cause detonation, and create porous hydrocarbon traps in the combustion chambers, valve and ports that screw up emissions and reduce flow, hurting power. These chemicals can also contaminate catalytic converters making them lose their effectiveness. These friction modifiers also are prone to shearing down and wearing out over time, losing their effectiveness.
Nissan, in their search for improving oils frictional properties, figured out a way to substitute ultra hard nano particles for the normal chemical friction modifiers adding some interesting molecular twists. Again due to the convoluted nature of Nissan’s white papers and patents, its hard to guess exactly what the nano particles are but they are defiantly an ultra hard industrial abrasive or bearing type ceramic and probably at least in part, nano particles of industrial diamond!
Why would Nissan put abrasives or chunks of bearing material in its oil? Well you have to consider some things about nano technology. The unit of measure here is called a nanometer or one billionth of a meter, that’s pretty darned small. A nanometer sized particle is much too small to be seen by the naked eye. For instance a water molecule is somewhat less than one nanometer. A typical bacterium is just less than 1000 nanometers and a hair is 100,000 nanometers thick. In the world of physics, weird things happen when particles are this small. The particles of the diamond/ceramic are so small they mix with the oil and stay suspended as they are hardly affected by gravity and molecular forces called van der waals forces keep them apart. They also are undetectable to the naked eye and the oil still looks clear.
Nissans super oil is around 0.5% nano particles by weight. The particles are probably around 10 nanometers in diameter, really very small! A certain percentage of the nano particles have to be carbon based, preferably single crystal synthetic diamond. The carbon content helps make the nano particles attracted to the low hydrogen DLC coating. Instead of making a slippery metallic film on bare metal parts like traditional friction modifiers, the nano particles act like atomic level miniature ball bearings, preventing metal to metal contact and reducing friction to previously unheard of levels. These nano particles are ashless if they find there way into the engine, making the oil low deposit forming for lower emissions. The Nissan super oil does most of its friction reduction in the valvetrain but it still helps in other parts of the engine, particularly in areas were metal to metal contact might occur.
In lab testing of test coupons, the Nissan Super oil with hydrogen free DLC coating had the friction reduced by 60-75 percent over conventional oil with no coating. This equated to a around a 40% reduction in total valvetrain friction in a real motor and a 20-25% reduction in total friction of the motor! This is a significant result which should show real gains in fuel economy and probably something like 1-1.5 hp per cylinder at high rpm over an uncoated valvetrain with conventional oil. If this is worth something to you then yes, the expense of the oil is worth it! Now the DLC coating still works at reducing friction with regular oil just not as amazingly well. Not using the Super oil will not cause you engine to wear out prematurely or anything like that but it probably will wear slightly more, particularly in the valve train, probably at a level that doesn’t matter much.
This leads to the next issue that has arisen with the VQ37VHR. When the engine was first introduced in the G37, there were complaints about a ticking noise coming from the engine, particularly after the first oil change. As common, particularly in these hard economic times, dealerships sometimes offer promotional oil changes at a very low price to help bring customers in the door. Typically these oil changes are a loss leader promotion were the dealerships might actually lose money just to attract customers. Naturally this results in the car getting the cheapest possible oil in the changes. If a G37 had low quality oil put into it, a customer might notice a very slight ticking noise eminating from the engine later. The noise is so slight that it can usually only be noticed when driving with the window open, close to a reflective surface like a hard wall. More G37 customers complain than 370Z customers probably because the G37 has superior NVH (quietness) to the 370Z and an Infinity customer is pickier.
It has been determined that the noise is caused in part by not using the super oil. The VQ37VHR engines VVEL system uses a reciprocating shoe that wipes back and forth across the cam follower instead of rotating like a cam lobe. This wiping action makes it difficult to establish a hydrodynamic film of oil in the interface between the shoe and the cam follower. Low hydrogen DLC coating is used here to both reduce friction, improve wear in this more difficult to keep lubed interface and to attract the super oil.
The super oil’s attraction to the cam followers helps cushion them hydraulically against the slapping action of the VVEL shoe, thus damping out the noise. Nissan’s TSB for the noise involves switching to the ester super oil and reflashing the engines ECU. Nissan has determined the revving the VQ37VHR without load helps contribute to the noise. What the reflash does is if you free rev between 1500-4500 rpm, the engines ECU will slowly return the engine to idle. If you free rev above 4500, the engine will return to a lower speed more aggressively. The noise is harmless and doesn’t affect engine life; just some people find it annoying. We haven’t been able to hear this noise ourselves in a 370Z’s that didn’t have super oil in them so it must be pretty minor, although these Z’s had intake and exhaust systems. Perhaps the best solution if you are bothered by this noise is to turn on your radio!
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07-30-2009, 01:46 PM
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