[BillA]

cf
you can get very different responses to your question
some here will attempt a differential measurement of an increment almost below the units resolution (coolant in-out), obviously they will be frustrated

I have not seen the units' inst., is a method described to determine the (gross) offset between sensors ?
(trim pot to 'zero' ?)
beyond that, which could be done at several temps if desired, an external reference is required which is outside of most users 'feel good' needs