Chat GPT 5.2 also told me to walk, but only because it made the assumption that because I was even asking the question, I must have multiple cars, and one of my cars was already at the car wash being washed. I clarified and said "I only have one car", and it replied that I obviously need to drive.
--- GPT 5.2
Walk.
Driving 50 m just adds friction: starting a cold engine, waiting, maneuvering, then immediately stopping again — all for a distance that’s ~30–40 seconds on foot. Walking is faster door-to-door, less awkward at the wash entrance, and you avoid lining up a wet car twice.
Only reason to drive that distance: you need to bring the car there anyway (e.g., self-serve bay where the car must be present). Otherwise, walking wins.
--- Me
I only have one car
--- GPT 5.2
Then you obviously drive — the car has to be at the car wash to be washed
The problem is that by specifying this, you have tipped your hand that there is something strange about the plan to walk. I think this is the original problem too: the question implies walking is even an option.