This site is handy and informative - http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqcode.asp?mode=nml

If you're on a phone (I'm hoping that's the reason for the effortless grammar) - R means Resistor.

hey, whats the difference between bp6es and bpr6es? pepboys gave me bpr6es......

R's have a resistor in the plug that, for what I've been told, reduces the amount of electrical noise given off by the plugs. I'm sure there's other reasons but that was the one I was given by a few people.

I've never run anything else but NGK's in my Z or any other L motor at that. They're not too expensive and don't seem to give me any issues at all.

Hope that helps

Jan

Edited August 26, 201212 yr by Pomorza

tracked it down, but thanks!