Outside temperature spins and car gets drunk

Good morning and a happy new year together. I have a problem with a drinking Cordoba Vario 6K GP01 (EZ 12/2000), 1.4L, 60PS engine ID AUD. For some time the outside temperature indicator spins. Here it was yesterday 2°C warm and the indicator wanted to convince me of 18.5°C. In the summer it happens at 20°C that the temperature indicator shows 3.5°C with *. The indicator basically does not matter, but the car has a consumption of about 13-15L/100km. Since it is from me and my Par However, this has not been noticed directly in short distance traffic. Is the outside temperature also passed on to the MSG and could the high consumption possibly be caused by a defective encoder, a partly “ice-cold, fat” injection? The display of the cooling water temperature “fits”, but if here also a double encoder, as e.g. with my A6 is installed, the display can possibly only be half the truth. I’m looking forward to hearing from VG Björn.