One eroded or fouled XJ spark plug can cause a loss of power and gas mileage, and eventually extremely expensive engine damage to your Jaguar XJ. You can easily avoid these problems, however, by keeping an extra set of Jaguar XJ spark plugs on hand for whenever the time comes around that replacement is necessary. Here at AutoAnything, we stock a large selection of XJ spark plugs to fit any budget and we guarantee you the lowest possible price with our one-year lower price guarantee. If you find a lower price for a year after your purchase, we'll refund the difference and throw in a dollar.