Car camping is much more of a gamble than backpacking when it comes to one's neighbors. I follow a couple of rules that seem to help. I do not car camp in free campgrounds if they are within 10 miles of a paved road or within 15 miles of a town where you can buy beer. I either choose a campground with a camp host and a fee, or I camp at a site so remote that only the most determined campers would ever go there. It helps a lot if there's nothing much to do when you camp there except hike, or possibly fish. I find that a site near a river or a creek is usually better than by a lake.

None of this guarantees considerate neighbors, but it certainly improves the odds.