Spark Plug thread continued...

[JLA M3]

Tried the following...

original, xr2cs, denso iridium (IX something) and now Xr4cs, the best so far is xr4cs feels good. Didnt really like xr2cs. Iridium was good but you had to carry a different tool to take them out as the orig tool doesnt work.

honestly, not much difference, I think all of them are pretty good already

[M3 Mitch]

So, for a more or less stock motor, is there any advantage in anything other than the standard Bosch plug?

In general I have found NGK plugs to be excellent and in Japanese bikes and cars have never found anything better. They also work right well in Chevy V-8's and I-6's. NGK's are frequently the best you can get for a lot of different motors.

In the VW 1800cc 8-valve motor, however, I have found that the Bosch 3-electrode plug (I forget the designation) gives a bit faster starting and slightly smoother running. I don't have a dyno so I don't know what it does for all-out power, but it has not made any noticable difference in fuel consumption.

Anybody got specific data or even anecdotes?