I think that due to the very small surface area of a plat. tip, it wouldn't be too hard to foul one out. I think they would be best for a car that is in PERFECT running condition. One interesting note, I have read in several places that they are not recommended for turbo engines. Don't know why, but I thought it was odd that they weren't. I have gone to Fastlane to look up sparkplugs for my Passat (turbo), and Bosch plats are not availible. On the other hand, when I looked up a Beetle it list both regular Bosch and Bosch +4s with the footnote "exc. turbo engs."
1994 MB E320 Coupe (199,500 mi)
1992 MB 190E 2.6 (173,000 mi)
1983 Porsche 911SC (148,000 mi)
2004 Volvo V70 2.5T (198,000 mi)
President of CT/Westchester Section