I changed mine out at 105K. A week before that, I was driving slowly in a school zone one day, in 4th gear at about 30 mph. All of a sudden, it just died on me, going down the road. I was able to just coast into a parking lot safely, and it did restart with quite a bit of cranking. When I pulled the plugs, every one of them had the gap worn out to about .085", where the stock plug gap for new ones is .045". It was no surprise at all to me once I saw that wear that the engine died. Plugs normally wear about a thousandth of an inch per 2K-3K miles (as in the gap widens due to electrode erosion.) There is a point at which the coils simply cannot make the spark jump the gap. Personally, I went with the Denso v-Power platinums, and I haven't had a problem since.

 

OEM is platinum hence the 105k service interval, platinum last longer than irridum, copper etc., check your owners manual.

 

I believe our coupes came with NGK Platinum PLFR5A-11 (Gap set at .044)
Gary

 

This is the plugs I recently purchased to replace my old ones. Hopefully it will be running smooth after I get it back from the warranty work done, oil in both #3 and# 6 cylinders