However, naive question, how can you be sure that a single temperature gauge is not over-reading?
I thought that was what everyone seemed to be overlooking, too. A failure of a Fuel Temperature indicator is annunciated on EICAS, but I assume this is for a total failure or an out-of-limits failure. Last week, I changed an engine oil quantity probe for underreading by 5 quarts. There were no annuciations of failure. We only noticed it because we had just topped up the oil and the reading was still low.