Engine Cleaner Hazardous Waste Residents may drop-off used or unwanted engine cleaner at the HHW Collection Facility. Never Dump Down the Drain Engine cleaner can contaminate waterways if it’s disposed of improperly. So never dump it in the trash or down the drain, even it’s unused; dispose of it as Household Hazardous Waste. Clean at the Car Wash Self-serve car washes have floor drains that are better equipped to handle contaminated water. Bring your vehicle to a car wash if you’d like to clean the engine.