I used to park in "The Garage at Post Office Square", on level 6 (the basement), they have a place that washes the car, vacumes the interior, they will wax and detail interior and exterior as well.. Of course you have to pay to park in the garage, and usually you would drive it down in the morning and they work on it during the day, then you pick it up when your ready to drive home. I realize your in backbay so this is probably not for you.. But they might have other locations I suspect, or maybe even go to your home on weekends etc. This is their website: Premium Auto Detailing - Home Their full package (interior and exterior) is $220 Premium Auto Detailing - Products Summary BTW, they now have 8 ChargePoint EVSEs on level 1 of the garage, as you drive in the Congress Street entrance: http://www.posquare.com/services.html#ev
Mat, the Tesla service guy, recommends the place across the street from the Tesla Service Center (sunshine?).
Hollywood Auto Detailing 45 Province St. Garage Boston (978) 360-3303 Recommended by the folks at the Mandarin Oriental. Used him (Frank Holywood) a few times. Does a great job!