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Hi people,
Ive got a M20b25 in my E21 and was just wondering what is the correct oil temp range the engine should be at,
the engine is standard and in not using an oil cooler.
On a cooler day it gets up to 90-95'C and on a really hot day it gets up to 110'C, is this too high?

Im thinking of adding the standard m20b25 oil cooler and the oil filter housing but some people tell me its not needed unless the car is tracked all the time.

Also does the standard m20b25 oil cooler have a thermostat in the oil filter housing?

Thanks in advance

These temperatures are just fine and pretty much the same as I'm used to with M20B25 or S14.

Of course, when pushed hard on a hot day it may run up further but from what I've heard no concerns whatsoever up to at least 130 degrees. As a failsafe an oil cooler would be good of course, that is why these were standard on E30 models with these engines.

Don't think I ever got over approx. 120 degrees, even on track.

Oh and the oil cooler adapter has a simple thermostat indeed, hiding behind a metal cap that is leaking in many cases haha. Replace the o-ring on it before fitting, saves a lot of hassle.

Thanks for the quick reply Jeroen,
Thats great! I dont want to add more things on the car if I dont have to,my friend who is an experienced mechanic told me that 110'c is too high and that it cooks to oil.

Thanks for the o-ring tip, ill replace it if i end up using the oem cooler.

cheers

My e30 325iA runs in the range from 85° to 95° celcius. 95° is some serious driving in the mountains.

Thanks for the reply,
Ok i see, im asuming you have the oil cooler on your e30 325i ?
My M20b25 came from a 1989 E34 and the car didn't have the oil cooler from the factory, now that its in my E21 323i and with a temp gauge and a 5speed it seems its running on the hot side. (in hot weather).
Im either going to install the standard OEM cooler or i might go with the aftermarket unit.
Thanks again

Yup his readings are with the original oil cooler.

correct.

thanks a lot