As wstar, and others have mentioned, there is a myriad of factors playing out here. Including that Nissan could have changed something that we do not know about in production. This means that certain model combinations as well as certain VIN numbers could be higher candidates for overheating. This is the reason documenting all matters we help us reach a better and faster conclusion leading to a resolution. What has yielded definitive results is that a properly sized oil cooler has solved the situation.

Having Nissan void a warranty because I installed an oil cooler is not a solution for me. If there are others installing an oil cooler, I would at the very minimum closely replicate or at least use the same Setrab oil cooler, or the actual Nissan oil cooler kit, should you end matters in a court dispute with Nissan. Nissan's sizing of the cooler core:

http://blogs.edmunds.com/roadtests/370z.oilcooler1.jpg

2009 Nissan 370Z Touring: Oil Cooler Install and First Service

If you are following the Edmunds blog above some of the most logical, and damning comments are those regarding the Sport Package option as you would think—at the very least—that the Sport Package would be inclusive of an oil cooler.

That final graph of 7AT vs 6MT only compares temperature and transmission. There are an untold number of variables not accounted for in that comparison that makes a generalized assumption of "the 6MT overheats more than the 7AT" incorrect. For example, 6MT owners may be the vast majority of the cohort who tracks their cars, they may be confined to a geographic location that has a warmer climate, etc etc.

All you can say is that, as a whole, 6MT owners have noted higher temperatures than 7AT owners. However, the results in NO WAY imply that under the same conditions, with the same driver, at the same RPMs, the 6MT runs hotter.

With regard to the transmission plumbing through the radiator of the 7AT, I don't know how that would provide any form of oil cooling for the engine.

Well, I got my gaskets in so there was no point sitting around the house any longer today. Hot and sunny outside, so I went for another oil temp test drive. Car's ambient air sensor in the info display was in the 88-92 range throughout the drive. Even Intake air temp (on a scan tool) was ridiculously high, from the hot pavement and heavy traffic. I saw that go as low as 105 on the highway, but it ramped out to the 150's sitting in dead stop traffic backed up at traffic lights. The heavy friday afternoon traffic was not ideal conditions for running the car hard, but on the other hand it gave me the chance to see if temps would run away shutting the car down into traffic after a hard run too.

First off, I ate some lunch at Sonic and left the car idling the whole time (about 15 minutes) to heat-soak everything. Oil temp stabilized around 210-215. Then I went out and drove on the small streets in stoplight traffic. I made my best effort to stay above 4K when it wasn't totally absurd to do so. I'm sure everyone thought I was an idiot cruising around at a deafening 4-6K-ish in 20-30mph steady thick traffic, but whatever ;)

I was only able to get up to about 230-235 doing this, because there were too many stops waiting on stoplight traffic. Of note, however, is that every time I got stopped, the car would bring itself back into the 220-ish range just idling in hot traffic.

Then I went up onto the highway and got a couple of hard WOT runs in (one on the initial onramp, and another shortly thereafter exiting a toll plaza). That got me back to 240-ish cruising on the highway. Then I went ahead and downshifted and kept the revs in the 5-6K range (with occasional peaks above 7K when passing other cars) for a solid 4-5 minutes. This gradually brought the oil up to 260, which is where I decided to call it quits. No sense going over 260 willfully, imho, that's getting into dangerous territory, but it seemed likely that I could have kept on pushing it higher if I just kept doing what I was doing.

At that point I grudgingly forced myself to just flip it into D-mode and drive light the rest of the way back home. D-mode w/ light throttle tends to keep the revs way down, around 1.5-2K-ish when not accelerating. The car quickly brought itself back to about 245-250-ish before I could even exit the highway to U-turn back. By the time I got back to a steady-state speed on the return highway leg, it was back to 240 again. By the time I exited and got home (the furthest point in this trip was perhaps 5 miles from my place), it was back to 230. Given the extreme heat-soak it went through, I went ahead and popped the hood and put a fan in front of the car to idle it back down. It came back to 215 in about 5 minutes and seemed to stabilize about there for a couple more minutes, so then I garaged it and shut it off.

My overall thoughts:

Yes, I need an oil cooler. Days like this (and much worse) will be the norm here during the summer, and on a longer drive, the way I drive, I can easily see myself being oil-temp-limited. That said, the temperature never ran away from me, even when 'stuck in traffic' and such. The oil temp was purely a function of how hard I was abusing the engine at any given time. At any time, if I backed off the revs and the throttle, it brought itself back down in temp accordingly. I'm still not panicked about it, but today definitely moved up my plans to get an oil cooler installed sooner rather than later.

Edit: also, given the variations in oil temp behavior I've seen on different drives in different climate conditions, I think climate differences are playing a bigger role in this than I would have initially guessed.

Not sure why you would think that the distribution of AT owners geographically would be any different than the distribution of MT owners geographically... my guess is that outside the pattern of more ATs in the US vs abroad, the distribution within the US (hotter areas vs not) would be similar for AT v MT.

I'm going to pull the excel spreadsheet with all the variables in the survey, and if you're curious you can go in and analyze. It includes variables for usage, ambient temperatures, transmission, miles on the car, and of course overheating patterns.

Sounds good. I'm not criticizing. I'm just saying that comparing two variables is far from a multivariate analysis of the issue. So, we have to be careful of the conclusions we draw. The geographic pattern is just a possibility...you'd be surprised about things you discover when you look into them. Maybe 6MT owners are clustered around race-tracks which may be more copious in warmer locations. Conversely, cold weather snow drivers may prefer the control of a 6MT over a 7AT. Heck, maybe dealerships around the country have different availability of each transmission that could cluster the results. Just hypotheticals...

Agreed. Next I'd like to see the relationship between ambient temperature and oil temperature. I'm curious to know if it's linear. e.g. if my car hits 240 in 70F weather, would I be at 260 with the same driving in 90F weather and 280 if it's 110F outside?

Given that the water temps never change on the gauge, the oil temperature variations seem to be indicative of the car's dependence on airflow around the engine. It would be interesting to know if a ventilated hood and/or more powerful radiator fans would make a difference just as the oil cooler does.

Spearfish... I'm too lazy to do the analysis, but here's all the raw data... as it turns out, country/state was captured by my survey software using the IP addresses... so if you want, you can actually compare region... not sure you need to though, because respondents actually included their hotest ambient temperature as part of the survey, which is the variable you're really trying to get at... would welcome anyone to slice/dice this

SurveyReport-1224538-5-8-2009.xls - FileFactory

PS I've got a "+1 rep" waiting for whoever analyzes this data ! :)

I drove on Thunderbolt today and did full 25 minute sessions. It was extremely hot today in Millville, my temp gauge was reading over 80 degrees. My oil temp did not go past 260 with the Stillen Oil Cooler. The car quickly cools off once the revs go down. The oil coolers do work. I doubt a factory fix would be as nice. Plus the majority of so called "mechanics" working at Nissan dealers are total hacks.

You don't think that 260 even with the oil cooler is excessive heat?

Still sounds pretty hot.

I wonder how many other cars have oil temp problems that nobody even knows about. How many sports cars don't have oil temp gauges and protective limp modes? Kind if makes you wonder.

Id bet the 350z had high temps during track days. It had no limp mode associated with oil temps. I tracked my 350z quite a bit...i always changed the oil before the event, then immiediately after.

.

I have to say that lately when people have been asking me about the Z (a lot of people!) I tell them about how fun of a car it is to drive, but they should NOT buy one because there is a serious oil overheating problem that has gone totally unaddressed by Nissan. Then I go on to talk about how they supplied all the cars to the review mags with oil coolers (implying they knew oil temps were getting too high) then left them off of the factory production cars. They look at me and say "ohhhh." That typically ends that conversation, as it should.

:) Yeah..

It's probably true that they sorta shot themselves in foot on this one by even including an oil temp gauge. On the other hand, they probably did it precisely because they knew this engine could be pushed to overheat, and they wanted the driver to have the feedback to know to drop the revs and save it, at least. Someone just dropped the ball along the way on the factory cooler option.