I also frequently rent a car, usually from Enterprise, when dropping a plane for service. I live in Atlanta, my preferred Diamond Service Center is north of Charlotte. I have found a couple of rides from other pilot friends, but a 3-hour round trip is a big favor to ask every time I need to go. I have had pretty good luck with Enterprise and I've used them all over the US. Their FBO group is pretty good and they even honor my Costco Travel discount code. One exception last week near Boston when I had to wait about 45 minutes for a car. Another time in FL they did not register that I had returned the car to the FBO and charged me several extra days of rental, but got that reversed.