[M-Steep]

Just finished a 3k mile road trip through Texas, Arizona, and New Mexico, and some ferocious heat - 121F in Mesa, AZ. Given our cars' reputation for running hot, I started out my trip worried about overheating, so I was really surprised by my oil temps when things got warm.

At one point, driving out of the mountains of AZ into the Phoenix area, I was pulling 6-8% grades at 80mph+, passing at 80-100mph, in 116 degree temps. Wonder of wonders, my oil temp at that point was holding between 210 and 220F!

For reference, I've got a 2009 335i E93, with factory oil cooler and Stage II PPK, so I do have the auxiliary coolant radiator and upgraded fan. In two years and 20k miles of ownership/driving (before and after the PPK II install), my oil temps have stayed at 235-250F, pretty much always. And consensus on the forum is the oil cooler thermostat opens at ~235F, which suggests that's the low end for oil temps. But somehow, the N54 has some mysterious extra level of cooling power?

I've searched the forum, and found several posts remarking on the same phenomenon. But the only documentation I've seen - if you can call it that - is the mention in the owner's manual that normal oil temps are 210-300F. There is, of course, some documentation of the various levels of cooling for the engine coolant, but really nothing to explain these extraordinarily low oil temps at ambient air temps of 110+.

So what gives? What is this magic cooling power, and can one of you clever hackers harness that power for the good, like on-demand extra cooling? I'd love to get some insight here.

[DanielGonz]

From what I've read, operating temps are around 240. Don't quote me though.

[SharkBait]

I have the stage 2 PPK as well with the better fan and extra radiator. I find that outside temps have little influence on my oil temp. My oil temp ranges between 240 and 250 whether it be 60 or 95 outside. In traffic or running hard, it will be closer to 250 and on the highway closer to 240.

I have noticed that if I put the A/C on (I typically prefer A/C off and windows open), the oil temp will drop a good 5 degrees within about 5-10 minutes. Pretty effective cooling fan!

[007_e350]

I've factory radiator and fan & I dont go above 250 under sustained hard driving..

[RobCrezz]

Is it possible that ECU runs a slightly richer mixture when oil temperatures get higher to lower combustion temperatures (and reduce oil temperatures as a result)?

Just speculating.

[Red_Bean_Bun]

Originally Posted by RobCrezz

Is it possible that ECU runs a slightly richer mixture when oil temperatures get higher to lower combustion temperatures (and reduce oil temperatures as a result)?

Just speculating.

Doubt it ....

[Dmacc]

Originally Posted by 007_e350

I've factory radiator and fan & I dont go above 250 under sustained hard driving..

Do some hard spirited driving up a 6+ mile mountain road at 14+psi, and start to watch the needle climb past 250*F

[BMW_Alex]

I use BMS thermostat device which replaces the factory spring operated one so my daily operating temps stay around 210 and only reached a high of 230 on very hot days of 90+degrees and in traffic. Only down side is i have to wait like 5-8 mins of driving before the jb4 kicks in, thats how long it takes for the car to reach 160 degrees.

[akotten]

Originally Posted by Dmacc

Do some hard spirited driving up a 6+ mile mountain road at 14+psi, and start to watch the needle climb past 250*F

Indeed. I run a factory like map at the track, and I can easily get to 270F on a 70F day. We'll see how she responds to this heat on Friday. Open track day with extended periods of driving in 88F weather.

[Jeff@TopGearSolutions]

Originally Posted by M-Steep

Just finished a 3k mile road trip through Texas, Arizona, and New Mexico, and some ferocious heat - 121F in Mesa, AZ. Given our cars' reputation for running hot, I started out my trip worried about overheating, so I was really surprised by my oil temps when things got warm.

At one point, driving out of the mountains of AZ into the Phoenix area, I was pulling 6-8% grades at 80mph+, passing at 80-100mph, in 116 degree temps. Wonder of wonders, my oil temp at that point was holding between 210 and 220F!

For reference, I've got a 2009 335i E93, with factory oil cooler and Stage II PPK, so I do have the auxiliary coolant radiator and upgraded fan. In two years and 20k miles of ownership/driving (before and after the PPK II install), my oil temps have stayed at 235-250F, pretty much always. And consensus on the forum is the oil cooler thermostat opens at ~235F, which suggests that's the low end for oil temps. But somehow, the N54 has some mysterious extra level of cooling power?

I've searched the forum, and found several posts remarking on the same phenomenon. But the only documentation I've seen - if you can call it that - is the mention in the owner's manual that normal oil temps are 210-300F. There is, of course, some documentation of the various levels of cooling for the engine coolant, but really nothing to explain these extraordinarily low oil temps at ambient air temps of 110+.

So what gives? What is this magic cooling power, and can one of you clever hackers harness that power for the good, like on-demand extra cooling? I'd love to get some insight here.

I've noticed when temps are 100+ my oil cooler seems to be keeping the temps below 230 also which I attributed to be normal.

My only theory suggest that because water temps might be on the rise (blindly to us without a diagnostic tool) that the coolant fans may be blowing extra air to the oil cooler.

I believe the Thermostat opens full around ~235 but prior to that it is partially open also. <-- dont quote me. (It's just a theory but it is open to some flaws and inconsistency).

[yarviinn]

I usually don't go pass 240. When I do spirited driving, it hits around 250.

[M-Steep]

Thanks for the replies, all.

My oil temps have always generally stayed at or below 250.

This is an issue of *lower* oil temps than normal - like 210-220 - when the ambient temp is 100+. That's a good thing, I would think. Just don't know how it's done?

It's as if the oil pump and oil cooler thermostat are variable and controlled by the ECU/DME, like the water pump and coolant thermostat, but I'm pretty sure that's not the case.

Interesting ideas of extra cooling in some situations from the radiator cooling fan, or maybe a richer mixture under some cases. I can't say I've heard the rad fan on at those times, but I'm driving at speed, and it would be hard to hear it. Richer mix, don't know 'cause I'm not logging any data.

Other thought I had was underhood temps maybe at or around 230, which causes the oil cooler thermo to stay open, even though the oil temp, as per the sensor, is lower than 230?

Just wish we knew what it was, so we could exploit it for good.

[BQTuning]

The cooling concept off the PPK is water to oil cooling. That why BMW never increased the size of the OC but rather increased the size of the primary rad, fan, and added an additional rad.

[M-Steep]

Yeah, I don't know that I saw this before the PPK II install, but I'm just not sure.

You're saying the primary aim of the additional rad and upgraded fan was to help keep oil temps down? That might explain it, but seems like the OC thermostat would constrain the lowest oil temp normally seen?

[shadow191]

Maybe it's just the large amounts of airflow. 120 is still a lot lower than 220 so at 80-100mph, that's a lot of relatively cooler air going over the radiator. 6-8% grade isn't a huge load on the engine either.

[bdaddylo]

Originally Posted by RobCrezz

Is it possible that ECU runs a slightly richer mixture when oil temperatures get higher to lower combustion temperatures (and reduce oil temperatures as a result)?

Just speculating.

The ECU regulates engine temp by adjusting the Air to Fuel ratio, so the hotter the engine temps are the richer the fuel mixture.

Also, your engine runs hotter when you're running at higher rpms. Next time try driving in a lower gear and you'll definitely see an increase in engine temp.

[BQTuning]

Originally Posted by M-Steep

Yeah, I don't know that I saw this before the PPK II install, but I'm just not sure.

You're saying the primary aim of the additional rad and upgraded fan was to help keep oil temps down? That might explain it, but seems like the OC thermostat would constrain the lowest oil temp normally seen?

This discussion came up sometime back as to why BMW would add an additional Rad rather than make a larger OC.

Well the facts are it works, in fact it works BETTER than the larger OC option. I know this cause on my previous E92 I upgraded to the Dinan OC with no PPK. Oil temps were the same, with the only difference is that the oil cooled much quicker.

With the PPK oil temps are sustained longer below thermostat regulated temps under harder conditions which mean less times the thermostat opens allowing more time for the oil to cool = cooler oil entering engine

[M-Steep]

That would make me happy, since I have the PPK added cooler, but doesn't explain what I'm seeing: oil temps at 235-250 in most situations w/ ambient temp *below* 100F, AND oil temps at 210-220 w/ ambient temp *above* 100F (and all other things being equal).

[buster84]

Another factor could be the type of oil you are using. When i got the car i was using bmw oil and noticed my oil temps at 240-250 on average without a factory oil cooler. I then switched to Mobile one, 0x40 European blend and on average my temps are 220-240. I was shocked to see such a decrease too. Temps outside were averaging 105 in sacramento at the time i did the change. It's also possible that the oil was just "Worn" out and over working it's self.

[AWil335i]

Definitely noticed my car running cooler last summer when it got really hot outside.

[BobS]

I think all the complaining of high oil temps is a little blown out of proportion. My car will get hot when I drive hard, but it comes right back to normal (210 ish) in short time. I only have the AR oil cooler in the kidney.

If you track the car, you'll def have oil temp issues, but just driving on the street? not so much...

[M-Steep]

Originally Posted by AWil335i

Definitely noticed my car running cooler last summer when it got really hot outside.

Yes! This is what I'm pointing out. But how the heck does it happen? I was really hoping someone could nail this definitively, 'cause it would be very cool, literally and figuratively, if we could switch the magic on at will.

Originally Posted by BobS

I think all the complaining of high oil temps is a little blown out of proportion.

Well, see, I actually am NOT complaining of high temps - I'm marveling at lower temps under harsh conditions (high ambient temperatures).