I do a buttload of biz on CL in a number of areas. Hell I even still meet females on CL from time to time. But the one unfortunate area I have to deal with every once in a while is the used car section. If you ever want to sell a car on CL then here is a good guide for you to save you time, money and brain cells.
1. Make sure to list your car at least 25% over your bottom price. Even if the car is worth $20,000 and you list it for $17,000 you will likely have a difficult time selling it because half the people with thing something is wrong with it and the other half will insist on negotiating for a lower price regardless of how low you list it. I guess they just need to feel like they got the best deal or want to influence people with their negotiating skills.
2. Make sure to take a many pics of the exterior and interior in good lighting because if you just take a few pics you will be asked a gazillion times for more pics.
3. Don't be too honest. Just like with political candidates and the news media most people want to be lied to in order to feel good. So if it burns a quart of oil between oil changes then fib or spin it and say it "just needs to be topped off once between oil changes". I am clearly too honest and I pay the price.

Never put things negative such as "it burns some oil" because you will fuck yourself.
4. Always go on the test drive. Always. I don't care if they are the whitest white people you have ever seen. These cunts will drive it like a race car if you are not with them.
5. If when they do get back from the test drive they start telling you all the negative shit they see with the car then just cut them off and say you need to go see another buyer unless they have the money you are asking for. I promise you these cunts are setting you up for a lowball offer. Don't waste your time.
6.Don't agree to meet anyone who has their "mechanic" or friend to check out the car. They will check every fucking god damn detail of the car. Cunts want a used car to be perfect and will point out tiny details that are ridiculous. Plus they spend an insane amount of time asking you questions and messing with the car.
7. Make sure the money they pay you is real cash with all the security features. And never accept a bank check unless you go to the bank together or verify it's validity some other way.