I hear what your saying. For the sake of generalizing for other shop owners, my viewpoint is not ideal I get that. I really hate to assume the worst of people however in my experience I try my best to avoid pitfalls. Time is money and unfortunately if I am getting a bad vibe from a customer then I will immediately assume things based on what I see. When I see a customer try to be pushy and want to do things on their terms without even giving me a chance to speak that sends a red flag. When they have their own oil, red flag. When they don't want to pay someone in the dead of winter to perform an oil service for them, red flag. Lets be honest here, the customer drives a BMW. Not a 1985 toyota corolla. The cost of a dinner in this city can exceed $30 easily. I am just making observations based on my area and my experience.
In regards to your question how do I find out if he needs our help? I really don't know. Actually a better answer is I really don't know without wasting my time and my patience.