My 07 Civic has recently been getting poor gas mileage. I know we are in the summer(or hot weather)blend of fuel and figured my MPG was down because of that, but at idle it was running a bit rough so I figured it was time to change plugs, wouldn't hurt since it's a new to me car. I went with the NGK Iridium Lazer or something like that. $14 a plug times 8. I picked up a little over 5MPG.

 

Never a bad idea if you don't know the mileage on the plugs. Just make sure you use the NGK or Denso specified by Honda. $14 from a parts store sounds about right.

The ones I swapped out in HCH2 #2 were absolute toast. Turns out it needed one of the coils replaced too.