Compressing AVI Files

I have a Mid 2011 27 inch IMac i7 running OS 10.9.2. I have been transferring AVI files from my car's dash camera to the iMac These files are typically about 2.5MB and I would like to compress them. When I run Compress File to produce a zipped version gof the file it appears to be the same size as the original. Is this because I'm doing something wrong or do AVI files not compress. Pardon my ignorance if this is a question that has been asked before.

Correct. AVI files do not compress. To make them smaller you'd need to either reduce their quality or their proportions. Neither is a good solution. Perhaps using an external drive for these files might be the best option.

Many thanks I had a sneaky suspicion that was the case.