top tip
if your bumpers are greying... weathered and old now forget products, or gels or sprays or groundnut oil or boot polish
get a heat gun and 30 mins and sort it.
Mine look BRAND new now.
It'll last about 1 month then go back to grey. You cant keep doing it either as it will damage the plastic. Old car salesmans trick to make the cars look like new 
suppose time will tell, although using poorboys trim restorer on this base is far more affective than on the grey!!
For the record
Going strong, black as new and this is a whole new year !!!