Dag-nabbit! Somehow my car caught a rock and it made a small crater in the plastic bumper covering. What is a good filler to fill such a crater? I thought about epoxy but am concerned that epoxy might not be practical for automotive applications (temperatures extremes, headwind buffeting, precipitation etc). Epoxy also often runs. Since this chip is on a vertical plane I need something that viscid like Spackle or toothpaste but obviously neither of these are suitable. Appreciate your thoughts.

You would need to use a plastic filler, sand and paint or just live with it. That is pretty small and you will get these at times. Fix it and you may have to do it again......and again.

3M Bondo seems to be what you're looking for, but then, after filling, sanding, and priming, you'll be able to paint and clear coat and then hope the colors match. Personally, for something that small, I wouldn't even start to think about that. If it is a lease car or something then I'd say wait until the lease is almost up and you're about to turn the car back in, then fix all of these that have accumulated.

Would you be referring to 3M 907 Glazing & Spot Putty? I've already got primer, factory paint, clear coat and a Q-tip so it might be something
I'd be willing to do. It doesn't seem like that big of a job and that darned chip grabs me and shakes me every time I walk past it.

Maybe. I see 31589 as a good answer. I don't see a 907 on the package.

Glaze is not used to fill holes. It'* used last to fill pin holes that are in the filler.