Every service advisor runs into them - the know-it-alls who have the answers to every question before they're asked. They can talk about electronic fuel injection, double overhead cams and higher RPMs at great length - and they usually do.
When dealing with a know-it-all, don't attempt to be a know-it-all in return. When you disagree with know-it-alls, they will immediately freeze any thoughts of purchasing needed repairs and won't budge. Then you've created a standoff.
What to do: Instead of telling the know-it-all why they're wrong, ask questions about their ideas. Remember that know-it-alls love to answer questions. As they look for answers, they might just discover that some ideas you present might be useful. In fact, they'll probably blend some of your ideas with theirs and think they came up with all of them.
Remember that the well-known motivational guru Dale Carnegie said that you're doing well if you can make people think that what you've said is their idea.