Z3 Engine coolant

My engine replacement just keeps getting worse
I finally got my car back after a brand new rebuilt engine, 2.8, was put in
i just turned 200 miles on it
Checked the fluids and realized BMW anti freeze was not used
generic i suspect
Does any one know how bad this is
Should i flush and redo?
Temp gauge is not running hot, but sure does blow real hot air from the heater

Well mine doesn't overheat but it also blows extremely hot air, even during the winter. Maybe this is a BMW trait...


But, I've used non-BMW coolant and didn't have a problem with it, even during a Driver's School. I don't know if that has something to do with it being a different engine, but if you're unsure, a coolant flush wouldn't hurt a thing. Besides, it's cheap insurance on a fresh motor.