Oil choice based - operating parameters - temp G35

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My primary car is a G35 which now has 150K miles. I have done a few UOA's on it that show that M1 0w40 is good for about 6K, and I am comfortable with that. I am getting ready to send in oil from a 4K run on PP - I assume it will be fine as well.

I have been going backwards with this according to common convention. When the car was new I ran M1 15w50. I did a lot of track days and a lot of trailer towing. Then after spending more time here, I switched to M1 5w30 - running what the manual called for - and got annoying (not in my head) top end noise. I then ran M1 EP 10w30 for a while (still with noise). At around 50K I switched to M1 0w40 exclusively, until about 120K after which I have been going back and forth between M1 0w40 and PP 5w40 based on what is on sale.

Every so often I hook up my Consult II type scanner and watch things. What I have noticed over time is that my oil temp at 82-85mph on the highway (without trailer) is between 114 and 116c. When I am driving aggressively I see temps consistently in the upper 130s. In the mountains when I am driving aggessively and in 3rd gear temps are mid to upper 140's. This has been exactly the same with all the oil weights that have been mentioned over the life of the car. The car has a factory oil to water oil cooler/warmer. The coolant temp usually stays between 85c to 100c with rare exceptions (BTW my stock gauge does not move at all between about 80 and 105c). If I stop moving, or drop to idle speed, the oil temp and water temp will match each other after a couple minutes.

I have never looked at or logged oil temps on the track. I do know that the newer versions of this car limit RPM after the oil hits a certain temperature - leading people to install aftermarket oil coolers. I suspect that my oil temp is well above

So my question would be, oils seem to be rated at 100c, when Nissan designed this engine/car combo - did they plan for the oil to be thinner than the spec at 100c? I assume different oils that measure similar viscosity at 100c might not be similar at 140c?

Granted, this car has already made it to 150K with my abuse - it is probably a little late now to make any major changes, but aside from changing my driving - should I be changing my oil to something different? Also, I am curious why I have never seen the temperature change with viscosity that people on the board say should be quite obvious? Are some designs more prone to this?

My other thought is regarding adding an oil cooler (which I am not doing), did Nissan design this engine specifically to have the oil at 140c when being pushed - would cooling the oil potentially cause problems when spending lots of time between 5K and 7K rpm? Are people who are putting oil coolers on these causing other issues? If an oil cooler was added, should the oil weight be switched to something thinner? The ECU doesn't have the ability to monitor oil pressure other than low/not low - so I can't measure it.

I almost always am on BITOG with a phone - never with a keyboard - so watch out!
 
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Frankly I would keep doing what you're doing.

PP 5w40 and M1 0w40 have almost the exact same HTHS meaning that in operation they are virtually the same viscosity.

The VQ37 motors were more prone to overheating because they were obviously being pushed to the max by Nissan.
 
Its too bad you can't fit an oversize oil filter on that 3.5 motor and then maybe fill it just a little over the dipstick line.

I'm thinking if you can get an extra 1/2 qt of oil in there it may stay a little cooler?

Anyone thoughts?
 
There are some nice oil cooler kits out there. Some are a little too much and the manufacturers tend to have a range of cooling capacities with that in mind.

I'm certainly not afraid of using 5w-30 in my G37. If I were to add an oil cooler, I'd almost certainly revert to 5w-30 immediately.

As for temperature change with viscosity, do remember that a thermostatically controlled oil cooler will skew one's observations. On the old Audi, one had to really pay attention to notice and watch for other variables. The rate of change of oil temperature was affected much more noticeably than the change of temperature itself, though that was there, too.
 
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