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."

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member