Actually, I had installed indoor/outdoor carpeting on a covered porch in a former home...the pile is synthetic, and resists dirt far better than standard indoor carpeting. Plus you can just hose it down when you want to clean it up, and it dries quickly, and won't mildew.
Not sure how well it can withstand the more caustic fluid discharge from automobiles...
I'm planning on getting my garage done soon, but I will go with the professional aggregate floor coating instead of carpet. It is sealed, so oil and other fluids can't penetrate, and you can hose it off. And unlike smooth concrete, it's not slippery when wet.
Don't really need a heater in my garage here in Texas, but I wish I had A/C put in when I built the house...but at least I did put in a ceiling fan...
