Dash Cams are a waste of money, do this

If you want hd with a high fps class 4 won't do it.

More important for a dash cam is the type of memory. With the constant looping a tlc card will die quickly.
https://www.mydigitaldiscount.com/everything-you-need-to-know-about-slc-mlc-and-tlc-nand-flash.html

 

Yes it will. I do precisely that, and do it with a class 4 card. My dash camera does 1080P at 30 fps and 720P at 60fps. Both settings work just fine.

 

If I format and record on a SD or mini SD card over and over and over again, will it eventually degrade the quality of the video?

 

There won't be a general drop in the quality of the video such as a lower frame rate or less resolution if that's what you are wondering.

Cards only allow so many write operations and will eventually fail. Once a card starts to fail it may just stop working at all, or there may be some bad writes that result in a corrupt video file. Usually they just stop working and you get an error message on your camera screen.

If there is a corrupt section in a video file you may get a skip in the video. Most video rendering software is smart enough to try to scan forward and recover if it can. But it's also possible the video won't play at all.