CAR is an archiving utility, and its associated .car file format. It is part of CarComp, a collection of utilities that was distributed as shareware. CarComp is apparently also the name of the company that developed it.
CAR stands for something along the lines of Compressed Archiver. Despite the name, .car files are not compressed. It's expected that you might compress them with Gzip or a similar utility, in which case the .caz file extension is suggested.
.car files have no signature, and can't easily be identified from their contents.
- CarComp (1994?) - Includes binaries for DOS and Sun/SPARC.