Mine sits right in the middle (between O and R). Never changed from the day I got it.
I'm thinking that the cause may be the cooling system not being flushed/ maintained.
Hector
2003 Rally Red Mitsubishi Evolution VIII
257HP/259TQ
2005 Lapis Blue Mazda 6s
RET: 00 Cabernet Red Ford Contour Zetec ATX SUPERCHARGED
160HP/141TQ