have a 2002 buick century ....temp gauge fluctuating over too three qtrs then back down too halfway when car isnt moving.....also change oil soon light staying on for like 60 seconds or more upon starts... I would like too know if these things happening are normal....car has 51,000 miles and has had 1 radiator flush recently...i am concerned due too all the problems GM has had with dexcool....Should i be concerned?