I own a 2014 Thor ACE - V10 - Appox 22k miles. Several months ago I noticed a carbon spot on the dip stick (about 18 inches up from the full scale). The engine runs great... just wondering is this common, or raising a flag for future problems?
I've seen this on many dipsticks that come out of engines that have the dipstick tube close to the exhaust manifold. If you could measure, you would find that it is right at the manifold. If the dipstick is not used frequently, it can "coke up" making it hard to get in and out.