DIY N54 Oil Temps and Thermostat

[N54_Gang/KR]

Topic: Considering Reinstalling an Oil Thermostat – Worth It?

N54 Oil Temp Management – With or Without a Thermostat?

Hey everyone,

So all of my friends and acquaintances running N54s have oil filter housings with thermostats installed.

Last summer, I got tired of constantly fighting high oil temps—especially how stubborn the temps were about coming down. So I went with a plate-off block and have been running the oil cooler fully open ever since. It definitely helped keep things under control.

But recently, I’ve noticed that almost everyone I know has gone back to using a thermostat setup, and I’m still the only one running without one.
That got me thinking... should I reinstall a thermostat?

If I do, I’m planning to go with the Moselmann oil thermostat—the one that opens around 85°C.

What I’m wondering is:
Is there a noticeable difference between running the cooler fully open versus having a thermostat that opens at 85°C?
From a performance or engine longevity standpoint, what are you guys seeing?

Would love to hear your thoughts and experiences. Appreciate it in advance!

P.S.
Currently running a 550whp setup.
It’s a Stage 2.5ver build with a Walbro low-pressure fuel pump, Vargas FRB+ turbos, and a Precision Race DI methanol injection kit (photo attached).

 

[oVeRdOsE]

engineer explained (youtube) just made a complete video about oil temperature and thickness.

- too hot you might have more metal metal contact.
- too cold, flow issue and lubrication properties not met . on n54 I wouldn't really be worried, the moment you wait to get the temperature high enough before wot.

 

[wheela]

engineer explained (youtube) just made a complete video about oil temperature and thickness.

- too hot you might have more metal metal contact.
- too cold, flow issue and lubrication properties not met . on n54 I wouldn't really be worried, the moment you wait to get the temperature high enough before wot.

View attachment 112485

Do you have a link to the video you could share? I'd be interested in giving it a watch

 

[oVeRdOsE]

Do you have a link to the video you could share? I'd be interested in giving it a watch

 

[wheela]

Thank you sir! I'll give it a watch

 

[N54_Gang/KR]

engineer explained (youtube) just made a complete video about oil temperature and thickness.

- too hot you might have more metal metal contact.
- too cold, flow issue and lubrication properties not met . on n54 I wouldn't really be worried, the moment you wait to get the temperature high enough before wot.

View attachment 112485

Thank you so much — your help really means a lot to me.

Aftermarket parts are great, but at the end of the day, a car is the result of countless tests,
built by a team of engineers, PhDs, and experts working together at the manufacturer level.

There must be a reason why they decided to include things like a thermostat.
It’s all part of a carefully engineered system.

 

[Traf]

Don't over analyze it, yes an external thermostat is almost always worth it, having no thermostat will lead to temps dropping when cruising.
Aim for 100 to 110°c of oil temp when loaded, i would get a 95°c thermostat or something like that, 85°c is a bit too low.

 

[CalvinNismo]

The Mosselman is a nice piece, nice machinework, and tried and tested. I also like the look of the Improved Racing one with -10 lines. That would be the one I would go for if I change from my standard thermostat, but I want to have the standard thermostat as a data point for comparison first (new oil cooler setup, with -8 lines).

Oil Cooler Adapter with Thermostat for BMW Engines

European customers: Click here to purchase directly from our partner in Germany , 55parts.de Precisely control oil temperature on BMW N20, N26, N51, N52, N53, N54, N55, and S55 engines. See application notes for more. Built-in high-flow thermostat improves oil flow and cooling performance while...

www.improvedracing.com

 

[JohnDaviz]

Thank you so much — your help really means a lot to me.

Aftermarket parts are great, but at the end of the day, a car is the result of countless tests,
built by a team of engineers, PhDs, and experts working together at the manufacturer level.

There must be a reason why they decided to include things like a thermostat.
It’s all part of a carefully engineered system.

It depends on your driving profile. If you are only racing.. you don´t need a thermostat.

If it is your daily with short trips daily, stock is good.
If you only go long trips or cruises or for pulls, 85°C is perfect.

The issue with 85°C and short trips is that you will not get your oil hot fast and burn off water parts in the oil. You get that slug on the oil cap.

I have the mosselmann thermostat with 85°C as i am only driving longer trips (minimum 20-30 miles per direction) so i am sure that there is enough time to burn off the water in the oil.

You don´t need to aim for temps above 100 degrees celsius at all if you do what is necessary for burning off the water.

 

[N54_Gang/KR]

It depends on your driving profile. If you are only racing.. you don´t need a thermostat.

If it is your daily with short trips daily, stock is good.
If you only go long trips or cruises or for pulls, 85°C is perfect.

The issue with 85°C and short trips is that you will not get your oil hot fast and burn off water parts in the oil. You get that slug on the oil cap.

I have the mosselmann thermostat with 85°C as i am only driving longer trips (minimum 20-30 miles per direction) so i am sure that there is enough time to burn off the water in the oil.

You don´t need to aim for temps above 100 degrees celsius at all if you do what is necessary for burning off the water.

"I built an AMG-killing machine to take on reckless drivers who act cocky on public roads, like those in AMGs. I've actually put a lot of them in their place.

These days, I'm seriously considering going with a big single turbo setup. Right now, I'm running a VTT FRB+ turbo with a methanol kit.

I mainly enjoy spirited driving on public roads, winding mountain routes, and occasionally on track days. Honestly, I haven't really felt inconvenienced by the lack of a thermostat.

But after learning more about visual/audio data and the effects of oil viscosity, it's become a really fascinating subject!"