From what a mechanic told me when I installed a 325i radiator into my 1971 BMW 2002; As long as it is running in the correct range you will be fine, and colder coolant temps usually translate into more power (density of air greater). My temp gauge sits right on top of the blue which is perfect. Hope this helps

87' Raider: off road package, rebuilt engine with (new) stock tires and alloy wheels but otherwise original.