Sell the benefits of your carwash. Don't tell them they need service they won't go. Tell them a dirty car is an extension of your personality. There's no reason we can't sell the public on this. Customers want longer hours.
Customers have concerns about obvious tipping requirements.
There is a difference between advertising and sending coupons in the mail. Customers who have equipment concerns generally have concerns about exterior drive-throughs. You need to establish equipment standards as an association. You also need to communicate that equipment has changed in the last several years. Signage is important.