Spark Plugs

[LawrieS]

In my car currently are NGK BPR6EFS, but all I can see recommended are NGK BPR6EF, it does have the tapered seats.

The difference is in the reach, BPR6EFS is 17.5mm BPR6EF is 19mm.

Please excuse my ignorance, but which should I use, it's been running perfectly fine, what difference would the reach make?

Thanks

[LawrieS]

Just in case anyone else comes across this thread, it turns out the information from the website I was looking at was incorrect, there is no difference in reach between these parts (http://www.gsparkplug.com)

The response from NGK was;
BPR6EFS and BPR6EF are identical in thread reach. The difference is that
BPR6EF is a 'V' groove plug (there is a 'V' shaped notch in the tip of the
centre electrode which forces the spark to the outside edge of the ground
electrode), which provides slightly improved combustion quality.

You can use either, but the 'V' groove plug would be better and is our
recommended plug. A further improvement would be to use Iridium plug
BPR6EFIX-10, 94658 - which offerers even better ignition quality and
improvement in combustion. If you do go for the Iridium plug, the
electrode gap would need to be reduced from 1.0mm to 0.8mm - being careful
not to damage the fine Iridium centre electrode tip.