Installing a water separator filter kit will not affect warranty as it works in conjunction with the original filter. It does not replace the original filter. There may be some reluctance by some vehicle Dealerships to alter the vehicle from standard but we supply our filter kits to a number of dealerships around the country. The fact is; if you get contamination in your fuel system; there is no warranty. We recommend you discuss installing an additional filter with your Service Manager, & explore the “what if’s” with regards to fuel contamination damage to your vehicle. A Service Manager with common sense will see that you are far less likely to incur expense with a Diesel Care kit fitted.