Mines sits below R on the guage constant when im out and thats just the way it is
Some are different but i wouldnot read too much into what that old 15+ year old guage is telling you
Ive also got a racetech watertemp guage in-car just to make sure , sometimes i ponder ditching my water off the turbo , because i feel this does add a bit of heat and stress to the system , but who knows