I had this on a couple of IS's i owned and to be honest it didn't cause any issues over the 10 years i owned them but managed to reduce the noise quite a bit. What i did do tho was i always changed the oil on a 6 monthly basis (this was back a few years when oil was relatively cheap) and during the oil change i would always run an engine flush through at the same time (Wynnes engine flush, smelt a bit like paraffin?) - 20 minutes at a higher rev than tick over. Whether it was placebo effect, it did reduce the times it rattled, but as it's a noticeable noise i would say yes it was effective reducing it down to once or no rattles at all in the 6 month period between changes. I seem to remember it did not remedy it immediately as it was over a long period of changes but i had always used an engine flush on all cars so carried on with the IS's. Yes, petrol and oil have cleaning additives but i was used to doing it for relatively little expense. I always used Castrol Magnatec which then changed to start /stop.