My silver/grey KJ has oxidisation on all exterior plastic. I was told that, after cleaning, use a mixture of WD40 and Silicone spray and rub in thoroughly. I did this to the spare wheel carrier and it came up very well but after a week started to tarnish again and look dull. My local automotive paint shop has showed me numerous products to clean and polish plastics and my Jeep agent has told me of other products which all seem to be like cut-n-polish or different types of silicone based waxes. I've tried a few but I think the WD40/Silicone lasts better. Does anyone have any "secret recipes" they have found to last?