…should you use interior or exterior paint (and primer) on the drywall?
Former housepainter checking in.
We always used interior latex.
Former, occasional and future house painter here. I would recommend both primer and indoor latex for the inside of a garage.
Right, I apologize. The primer is implied. 
you’re painting the inside of your garage? how anal is that? at least have some fun with it! Get some explosives, put a five gallon bucket in the middle of the garage floor. Light the fuse, and run!!
Yep, use interior.
Exterior protects from weather and sun.
My grandmother owned rental properties, and I helped her with painting and papering for nigh on to a decade, and we never once used primer. Whenever we had to paint, we’d wipe the walls down if there was visible dirt, but otherwise just slap a coat of Sears interior semi-gloss latex on 'em. We never had any problems. The only time we had to repaint between tenants was if they had in some way damaged the walls.
Am I missing something? I always thought that primer was just for walls which had never been painted: i.e bare drywall. Are you really supposed to use it every time between paint jobs? Why did I never see any problems caused by not using it?
Collect leftover paint from your own house and the neighbors. Make sure it’s all latex (it can be interior or exterior),mix it all together and paint the garage for free.
The OP asked whether to use it on drywall. He made no mention of whether there was already paint on it. I would have thought not, it being a garage. Since it’s more outside than the rest of a house, it would be a good idea to use a primer/sealer to protect the drywall against moisture and humidity. On other indoor jobs, it’s not necessary to use primer, except in the case of where you want to change the color of a room from dark to light. The primer serves to cover up the dark better than attempting to apply multiple coats of paint, only to find that you can still see the old color underneath it.
FYI, it is bare drywall, which was mudded and taped by the builder ten years ago. So I definitely need primer.
Thanks for the responses. Interior latex it is.
It doesn’t really matter. I would think more about the finish. For a garage, I would use either semi-gloss or gloss for reflectivity and ease of cleaning.