What is the difference between Manufacturing/Design process of CMOS IC for Automotive Grade 1 and Grade 2
Having decades of wide-temperature PCB and silicon design experience, I'll provide some opinions.

Usually I'll run simulations at 125C or 150C (if the semiconductor foundary models can be trusted to 150C), just to ensure there is functional and waveform margins; should a waveform turn ugly at 150C (e.g. not full swing, or imbalanced slewing, or overshoot rears its head) I'll examine the circuit and look to cure the ugliness. In this manner, I avoid warrantee failures out in the field. The customers stay happy and trusting the ICs.