In one thread someone mentioned it should run close to 90. During the summer I run under 80, usually about 75-78. During winter, probably around 70 if that.

I never had good heat during the winter. On a recent all highway trip I checked my milage and its poor. About 16 all highway. And the engine temps never got very warm. Again around 70 or so. And I have no viscus fan right now!

So I put a piece of cardboard in front of the radiator. I now run just under 100 and my milage is about 18.5 and climbing as I average more fills.

So clearly my t-stat is bad. But I am also wondering what I should see temp wise when I replace it.

Just not looking forward to adjusting lambda AGAIN, this time at true operating temperature.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car