I have a 1985 380SE. I asked the same question a few weeks ago and it now my understanding that it has to be left on celcius. It did not read in fahrenheit until 1986. Mine is useless as far as I am concerned. I know that 0*C = 32*F and that 32*C is something like 100*F, and 10*C is something like upper 40s to 50*C, but that is about it. As far as me using it as measure the exact temperature while I am driving, it is worthless. Perhaps after time I will get used to it and learn the celsius scale?