if you’re wanting to wash it at home,

The AI should absolutely understand the implication that you want to wash your car at the car wash, not at home. The prompt is clear about that, even though it is implied.

“I want a hamburger. McDonald’s is three miles from me and Wendy’s is five miles. Which is the cheaper place to get a burger from when you consider the distance to each?” is not an exact analogy, but the point is that it should be ABSOLUTELY clear that you do not wish to make your own hamburger. Any response that discusses that as an option is ridiculout, unless maybe it’s one of those options-at-the-end thing LLMs love to do - but it has no part of the main answer at all.