Engine warmup - oil temp drops when driving

[strokemycocktus]

I am trying to figure out if my cooling system runs properly. When I start the car in approximatey 8C and start driving it heats up much faster when I get stuck in traffic early rather than when actually driving. For example, when I start off into traffic and mostly stop and go, the car hits 100C after 10-15 min. After I get out of traffic it instantly drops to a little over 75.
When I start off in the evening and drive in very little traffic, it takes much longer to reach 100C. Is this normal or should I check my thermostat? All my other cars built up temperature rather constantly, with no drops.

[EJT86]

check your belly pan condition. only time my oil temp dropped a bit while driving was in winter after my belly pan was ripped off. without it the oil cooler gets a ton of cool air and cools off quicker

[msan]

seems normal from my experience. The M3 oil temp does fluctuate and reflect precise temp, it's not like a Toyota where it just stays at the middle line all the time even though the real temp maybe be fluctuating a little bit.

[strokemycocktus]

msan I know, but it's sometimes a ~20 degrees drop after I move off from stop and go traffic. Are the fluctuactions you mentioned that big?
EJT86 Thanks for the info, I will check it. What should I look for exactly? My underbody was checked recently as I have cracked the left panel (the small one) and the workshop did not report anything wrong with the belly pan.
Does the oil cooler have any type of thermostat?

[EJT86]

Originally Posted by seevin

msan I know, but it's sometimes a ~20 degrees drop after I move off from stop and go traffic. Are the fluctuactions you mentioned that big?
EJT86 Thanks for the info, I will check it. What should I look for exactly? My underbody was checked recently as I have cracked the left panel (the small one) and the workshop did not report anything wrong with the belly pan.
Does the oil cooler have any type of thermostat?

Well my experience was that my center pan was gone completely so there was a ton of winter air to the cooler and it cooled the oil off more than normal. Once I reinstalled the pan it went back to being consistent. On the highway with lots of airflow it would run cool like in between the first line and center line. I’m not sure about the inner workings of the cooler so not sure where the thermostat is located if it’s anywhere near the cooler it would have to be after the oil leaves the cooler

[strokemycocktus]

That's not my case then. I manage to keep consistent temp value on a highway.

[Helmsman]

Certainly goes up in stop and go traffic while down at high way. 20degC however is much more than mine fluctuate, more like 90-100C. In my experience the temp meter is pretty accurate but you may double check with for instance Carly to make sure it works properly.

[roastbeef]

your car is behaving normally. nothing to be alarmed about.

there is a little bit of misinformation in here. the front felt undertray helps with cooling. having a missing undertray will actually cause the car to run warmer than normal. this is because instead of air being forced through the oil cooler and out the bottom of the undertray, the air simply flows around the cooler (less resistance) and out under the car. this makes the cooler less efficient.

the reason op's car heats up faster in traffic is simple, there is less airflow forcing air through the cooler.
if you look at the felt undertray from the side, you will see it is shaped like an airfoil. this causes a low pressure zone behind the oil cooler outlet, which encourages airflow through the cooler. there is also a shroud behind the cooler guiding the air out of the exit.
if you start the car and it is not up to full temperature once you get to a clear highway and get up to speed, it is going to take longer because the cooler is simply working at it's most efficient level.

[EJT86]

Originally Posted by roastbeef

your car is behaving normally. nothing to be alarmed about.

there is a little bit of misinformation in here. the front felt undertray helps with cooling. having a missing undertray will actually cause the car to run warmer than normal. this is because instead of air being forced through the oil cooler and out the bottom of the undertray, the air simply flows around the cooler (less resistance) and out under the car. this makes the cooler less efficient.

the reason op's car heats up faster in traffic is simple, there is less airflow forcing air through the cooler.
if you look at the felt undertray from the side, you will see it is shaped like an airfoil. this causes a low pressure zone behind the oil cooler outlet, which encourages airflow through the cooler. there is also a shroud behind the cooler guiding the air out of the exit.
if you start the car and it is not up to full temperature once you get to a clear highway and get up to speed, it is going to take longer because the cooler is simply working at it's most efficient level.

Wasn’t misinformation it was a personal recount of exactly what was happening to me. I said it was something to look into based on my experience. And the belly pan has basically a slit with a directed bend to the oil cooler vs it being wide open idk about summer and 90 degree but as I said this was January and 14 degrees so it had the effect I stated earlier

[Loki Motorsports]

Mine behaves the same as OP, But I do believe this is normal behavior for a engine with an oil cooler. I live up in Vancouver, WA... where this time of year the avg. weather temp is mid 40*F. In the morning on the way to work, it will warm up 5-10* while sitting at a red light, then stay the same until I come to a stop again and there is no airflow through the cooler, thus allowing the temperature to rise. On the highway this time of year, the oil temp will sit right around 175-180*F cruising in 6th @ roughly 65 MPH. If you are truly worried about oil getting to operating temp faster if you do a lot of highway on your commute or driving, you can always cut yourself out a piece of cardboard the size of the cooler during the winter, and zip tie it to the front. Blocking ambient airflow.

[strokemycocktus]

Thanks for the input everyone, it seems I am not used to a car with an oil cooler yet - it's my first winter with the M3. I was just worried that there is something wrong with my thermostat.

[dparm]

Also, these are not air-cooled cars.

[Loki Motorsports]

Originally Posted by seevin

Thanks for the input everyone, it seems I am not used to a car with an oil cooler yet - it's my first winter with the M3. I was just worried that there is something wrong with my thermostat.

Of course! It worried me for the first winter as well. You aren't the only one!

I've also read that there is a OIL thermostat in the filter housing, not sure if that's true or not... Because if there was, the oil would warm up gradually at a steady rate, then stay consistent, similar to the water cooling system...Not exponentially like it currently does. Can anyone clarify this and debunk?

[msan]

Originally Posted by Loki Motorsports

Of course! It worried me for the first winter as well. You aren't the only one!

I've also read that there is a OIL thermostat in the filter housing, not sure if that's true or not... Because if there was, the oil would warm up gradually at a steady rate, then stay consistent, similar to the water cooling system...Not exponentially like it currently does. Can anyone clarify this and debunk?

False information, the oil temp is taken by the oil level sensor.

See my post here

http://www.m3post.com/forums/showpos...7&postcount=81

[Loki Motorsports]

Originally Posted by msan

False information, the oil temp is taken by the oil level sensor.

See my post here

http://www.m3post.com/forums/showpos...7&postcount=81

Thanks for clarifying! Makes sense now. Only thing I noticed is that that PDF was for N52 engines.. I imagine the S65 uses the same sensor?

[msan]

They all use the same sensor