A quick look at your numbers shows an interesting ratio
Actual Reading ratio
90 125 1.39
80 110 1.38
70 85 1.21
60 75 1.25
Its not linear but up beyond 80+ it seems fairly consistent.
The temp gauge works onmeasuring the current flowing through the sensor, so to have it over-read there is too much current. You could reduce it by putting a resistor in-line with the wire to the sensor. What you will need to know is the resistance of the sensor at, say 90 to do the calculation.
If you use a multimeter to measure the resistance (R) then the in-line resistor would need to be 0.38*R
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