I guess I've determined that my '88 740 n/t wagon has a bad thermostat that is causing overcooling, so I've started looking around, on the internet, in catalogs, and in the phone book for a new one, and to my surprise have found that they are available with different ratings for the temperature at which they open, and I don't know what temp to get. I suppose one way around the question would be to get the OEM one from the dealership, since they presumably know what the correct temperature rating would be, although theirs is (of course) the most expensive. So, what temperature rating does my car require, and what are the good and bad consequences of installing one with a higher or lower rating?