Most new customers wanting to use Evans will need to remove the existing water based coolant from their system. To Gain the maximum benefit from Evans we recommend that no more than 3% residual water is present in the coolant. To help achieve this we have formulated a hygroscopic Prep Fluid designed to flush the system before adding Evans.How Does It Work Fill the freshly drained cooling system with Evans Prep Fluid and run the engine up to normal operating temperature. The hygroscopic fluid will absorb any residual water and flush out any loose deposits.What should I do with it then Once the Prep Fluid has been drained from the system, store it in an air tight container as it can be used several times.Available in 2litre or 5 litre (Please call if you require 25 Litres) About Evans Waterless CoolantSince the 1930's engine coolants have been based on a mixture of water, ethylene glycol (antifreeze) and corrosion inhibitors. These mixtures have inherent physical and chemical limitations