Is there an easy way to tell if I should use a regular sparkplug, or one that's hotter or colder? I'd like to be able to tell before I buy, so I don't waste time. I'm after fuel efficiency, driving long miles at highway speeds. Thanks!
Jae

 

check your plugs, see what they look like and compare to these pictures

then deside

http://www.gnttype.org/techarea/engine/plugs.html