Chemical preparations for use in the servicing of motor vehicles, including chemical preparations for use in connection with engines and parts and fittings therefor (including catalytic converters); chemical preparations for use in connection with fuel; chemicals for rejuvenating and/or cleaning engines and parts and fittings therefor (including catalytic converters); chemical additives to fuel, oil and lubricants; chemical preparations for use in the cleaning of catalysts in or for catalytic converters