I add Power Service in the winter, just to give it the extra help. Car sits outside in driveway and plugs into a timer that even works sometimes. Probably doesn't need additive since most fuel I get is at Flying J truck stop and they seem to add conditioner as soon as it starts getting cold. Had injectors crack tested recently and one disassembled. Shop was impressed with how good it looked. Said I must be running very good fuel. No crude, no wear. I do run a can of diesel purge through the system about once a year.