John,
The Duratec in my 2012 +4 uses these platinum plugs. I've just replaced them in mine as the originals looked shot. There are previous posts on here to the same effect. The engine is designed to have a plastic cover but presumably (as mine has no cover) due to room restrictions and Morgan engine bay configuration, this is impractical (according to a few opinions.) Weather, wash and general wear & tear seem to have trashed the plugs. Some may be of the opinion that the plugs, though looking bad, still operate ok. This could well be so, however - I have found that since replacement the car starts better. Maybe I had a duff one - but it's worth mentioning that when running, the car was perfect and 'starting' was only affected noticeably but mildly (churning starter rotations as opposed to instant or near enough.)
The plug-change was at 10,557 miles using -
NGK: Platinum TR6AP-13 stock no. 5809
Hope this is of some use to you.
