Post this over on rec.aviation.owning to get an answer.

"Seagull149" wrote in message
ups.com...
Hi,

Our vintage aircraft are operated with an appr. 50 year old
oiltemp.gauge. Alas the sensorprobes have all failed.
In a test setting it was determined that the probe was of a PTC type
with the following characteristics;
T( in Celcius) R (Ohm)
120 151
110 145
100 138
90 134
80 129
70 124
60 119
50 113
40 108
30 99
10 95
We haven't been able to find a PTC sensor yet, anyone out there with a
good advice, because we would like to go on with the original
instrument,

thanks

Michiel

www.seagull-formation.nl