Material Instance Created in Car Model Prefab

I don't know why my car 3d model's mesh renderer creating own instances of all materials when I spawn it using prefab. Please check below image for the same: ![alt text][1] My environment models not creating own instances of materials but all cars models doing. I hope you are getting my point. Here I am attaching an image for car model import settings: ![alt text][2] **So I want to stop these new materials instance creation process** so I can do the following things: I want to change car chassis color runtime so I have created material for this purpose. But after spawning of car model, it has own material instance created at runtime so color changing not get affected in this case and I want to solve this problem.

I have created another demo project in that this kind of situation not get created. There is no new instance of material gets created within mesh renderer. [1]: /storage/temp/138997-car-chasis-materials.png [2]: /storage/temp/138998-car-model-12.png