Everyone with oil temp issues

rackley

That's because you have an AT car. Most or all of the evidence points to the 7AT cars not having the overheating problem nearly as bad as the MT cars. My buddy here on base has a 7AT and he cruises at 200*F and rarely hits 220 even with hard driving. My bottom oil temp is 220 and I go up from there to 250 before I pull over for fear of melting the engine.

7ATs do not seem to have the overheating problem nearly as bad. So because you have a 7AT without an overheating problem does not invalidate the experiences of everyone else with MTs who are overheating.

Captain Tuttl

What is the correlation between AT running cooler than MT?

Is it because on average, the shifts tend to be at a lower engine speed with AT vs. MT?

Or does the AT model have some additional cooling capabilities built in?

High oil temps with primarily the MT is a pretty significant data point.

spearfish25

I'm not sure that constraining the temps to the MTs is an accurate assumption. My 6MT has only hit 245 once and that was after spirited driving followed by gridlock traffic for an hour on an 80F day. Otherwise, we've had 70F weather and my temp hasn't gone above 220 even with aggressive driving. As someone (semtex or wstar) said earlier, the temps seem to be settling down a bit as the engine is breaking in. Perhaps initial engine friction is gradually being reduced with the added engine hours. I also did my first oil change with Nissan Ester Oil at 1300 mi. I'm at 1500 now.

travisjb

here's the data on 6mt v 7at oil overheating
Oil Temp Survey

spearfish25

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.

travisjb

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.

spearfish25

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...

travisjb

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 !

wstar

If there's any difference between 6MT and 7AT in this regard, it pretty much has to come down to one of a few things:

1) If the 7AT's fluid is cooled by the radiator (there are hard lines plumbed straight into the radiator from the transmission, IIRC, but I'll have to go look again or check the svc manual), this may have some sort of indirect effect on the overall cooling efficiency of the car, in some way that I can't imagine right now. Edit: confirmed this in the svc manual, TM.pdf Pg 295, we do have transmission fluid lines running to the radiator on the 7AT

2) It could be shifting behavior. Not user shifting behavior, but what Travis was describing earlier: the 7AT rarely if ever over-revs between gears on upshifts. You click and the revs snap down instantly. 6MT guys are seeing the revs spike a bit before dropping. Given that (as Travis noted, and I agree) the rise in oil temp seems to be affected exponentially by a rise in RPM, this extra time at higher RPMs near the top of the range could be having more effect than you'd expect.

3) User behavior, meaning that basically 7AT drivers drive like grandmas relative to how the 6MT guys drive. In the sense that almost all people who are tracking the car will buy 6MT this is definitely true on average. That aside, even on the street, most 7AT buyers are AT-type of people, and they just drive different, and will often use 'D', which keeps revs *way* down when you're light on the throttle, much lower than where I manual driver would usually hold them at light throttle. However, this isn't the case for me. I just came from spending 10 years behind a 6MT transmission, and I drive my 7AT as close to how you'd drive a manual as possible, and while I'll never approach full track conditions on the street (especially on the braking side of the equation), I'm running the car pretty aggressively.

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