Petrol forecourts with automatic car washes could become dry zones if water companies get the green light to impose a ban on non-essential use of water.
Two consecutive winters of poor rainfall have forced water companies to apply for drought orders, which could prevent car washes from operating.
A spokeswoman for BP said: "A ban on the non essential use of water would have a serious impact on trade. Not only would it affect car wash revenue, but there could also be an impact on other areas of business."
BP's car wash team were holding an emergency meeting this week to discuss how to maintain customer service.
Industry association Water UK said that there was a possibility that car washes that use water recycling equipment could be exempt from a ban.However, these systems are predominantly found on recent builds and not many older sites.