The University of Texas completed a study showing that a single home wash can leave scratches in your vehicle’s finish as deep as 1/10th of the paint’s total thickness. Hand washing, especially with chemicals that are not designed for auto paint like dish soap, can damage your finish. Moreover, uneven pressure from hand washing can place up to 100 pounds of pressure on your vehicle. That’s far too rough on car paint! It gets worse. Using improperly cleaned towels with accumulated dirt from other parts of your vehicle will scratch your paint. Finally, the average garden hose does not supply enough water pressure with the detergent action to avoid damaging a vehicle’s finish.