Plug Woes

The last few weeks have been a bit frantic with the Pathfinder. What started off as an occasional misfire that wasn't even detected by the ECU quickly became an AA recover and a few days at the local Nissan dealership in Sheffield. At one point I suspected a blown Head Gasket as the smoke being produced when I started up from cold seemed indicative.
As it turned out, thankfully, it was only a failed spark plug. The resulting unburnt fuel making it's way to the Cat and as that heated up, being burnt off.
I've since put a new set plugs in and gone for the next coldest temp rating to try and work better with the higher burn temps of LPG.
This failure was at 42000 miles and the plugs were only due for changing at 54000. Having done 9000 miles on LPG they had clearly expired before time. The gallery below shows the condition of the plugs as they came out

Pathfnder Spark Plugs