I had an all-too-familiar experience yesterday at a drive-through oil change shop. It started with just an oil change — the service I’d actually come for. Then came the suggestions: “You’re due for an oil system flush.” (I agreed) “Your fluids are low.” (Sure, top them up) “Your air filter is dirty.” (Fine, let’s replace it) “Your wiper blades are worn.” (Erm, okay…) By the time she suggested a coolant flush and a pricey replacement radiator cap (mine could start leaking, y’know!), I was...