do you ever know everything

I feel that in my industry that you can know everything but also you can not. I feel this way because you can know everything about cars but technology is always changing so you constantly have to learn more and more. For example I know that this is true because I know a lot about cars but we always have to hook cars up to the computer and see what the real problems are and not go off of a hunch. for this reason I feel that there is sometimes an endpoint to your learning every now and then because i can change oil thats never going to change.