Today, I've ordered a set of the wrong index spark plugs, to fit in my Insight.
Why? Well for a start, they were going cheap - but my decision was based on more than just that.
I understand the logic of indexing. I'm assuming that plugs A,B,C,D are all identical bar the electrode being 90 degrees different to the last, orientated to the thread. From reading here, it appears that virtually all insights are mostly B, or failing that, an A.
To me, that indicates that Hondas manufacturing was pretty precise, but the exact back of the engine for most engines is somewhere between plug A and B, nearer to B. The exact back could be up to 22 degrees off of where the plug electrode actually ends up before a different index plug would of been used.
Now in my logic, the idea of indexing is less about having then electrode at the back, and more about not having the electrode at the front where it would get in the way of the fuel air reaching the spark. So as long as the electrode is within the 180 degree back area of the chamber, the engine is going to run virtually identically.
My engine has Bs marked on it, and I've ordered a set of As. I should add, if the correct index plugs were easily available, I would have ordered them. These were much cheaper though. They are genuine honda ones.
Hopefully they will arrive tomorrow, and I can fit them at the weekend and report back. Fingers crossed my logic holds up.