I was just wondering what the effects would be, they are vitually identical. But obviously there is a reason there are two sets, trailing and leading spark plugs?

 

One has a pair of blue stripes. The leading (lowers) fire twice as often and are colder to disspipate more heat.

 

Blue = Trailing = Top
None = Leading = Lower

 

So it sounds like it could effect a misfire, rough idle. ect. due to a simple mistake. I was just wondering as far as preventative maintenance goes.

 

Go with all 9's and don't worry about it.

 

What happened did this thread get closed or something. Well anyways the stupid nuts at the autoparts store gave me the wrong advice said the 7eq go on top and the 9eq's go on the bottom, but actually on the plug itself it has a T and L. That's why I was wondering if it happened on accident could it be devestating on the engine.

 

 

Normally, the trailing plugs are colder (9s are colder plugs than 7s). If you swap the plugs you will have a hot plug in the trailing spot. That may lead to detonation. However, I think it is rather unlikely that you would have any serious problems for normal driving.

-Max