When I lived up north a ways, I could talk to my wife in the parking lot when she got out of work, from my house without a problem. (I worked 1st, she worked 2nd) total distance was just over 26 miles straight line (nearly 40 by road)
Could talk to her most of the way, but lost her for a few minutes when she entered a small valley about 15 miles from home.
Both radios were stock, the car had a mag-mount whip on it, and I had a home built 1/2 wave at home.
Often the problem with a CB is the other radio, I have a friend that lived 3 miles away, and I came in loud and clear to him, but he just barely cleared the background noise at my end.
Current set up is an old Uniden grant xl SSB, and a 102 inch stainless whip on the back bumper of my explorer. It gives good range, and is sensitive enough that I can pick up weak signals that people with more expensive antennas miss. And is both tough, and cheap enough that I don't worry about it when out beating on my truck.
Ken.