I've always thought I was pretty good at keeping an eye on my car. I check the oil, look at the tires, and pay attention to any new sounds. So I was completely shocked when a mechanic friend offered to do a quick scan and found a sensor fault that was slowly affecting my fuel economy and could have led to engine trouble. He explained that there are many issues you might miss during a vehicle check, especially if you're just doing a visual once-over. Things like early brake line corrosion, small fluid leaks hidden under covers, or suspension wear that doesn't make noise yet. It was a real lesson for me. Has anyone else discovered a problem they had no idea existed until a professional took a closer look?