As a retired lifetime
As a retired lifetime mechanic..i just warm it up & drain & refill my '05 matrix awd(90k)&'04 tacoma 4x4(190k) every 2 years.. I bought the tacoma used so i flushed & pulled pan at 140k...use Castrol import fluid..no problems..p.s..i drain & refill coolant same time..yea..its all spotless & trouble free..