Indexed Spark Plugs

barnum · 11-02-2011, 06:08 PM

I have two 2001 MT insights that are due for spark plug replacement. I was wondering if indexed plugs make a big difference in the mpg? I know that the manual calls for them....but over the counter part store plugs are not.

Eli · 11-02-2011, 06:42 PM

Define a big difference. If it costs even 1MPG, would you want to risk it?

Every little thing adds up. Indexed plugs could be 2MPG, Underbody aero panels could be another 2MPG. Now you're at 4MPG loss. Throw in non-LRR tires, and you're at 10-12+MPG. It all adds up...

Just buy the indexed plugs. Or index aftermarket ones yourself.

barnum · 11-02-2011, 09:58 PM

Thanks Eli....yes all of it does add up.,,,but as these cars get older I'm just looking at what parts (the few that there are

) I can get locally. The nearest dealer is 150 mi away.I have gotten parts from the online dealers....and have to wait for shipping. Both cars deliver very close to specs depending on the tires I have on them. I am not a hypermiler....so I could live with 1mpg....I am the second owner of both cars and they might outlast me

barnum · 11-11-2011, 05:21 PM

I decided to get the indexed plugs. Turns out both cars are all B. One has 113,000 the other 120,000. The plugs looked good that I took out...with a bit more of a gap.We have blizaks on one for winter driving....so the mileage is averaging 50mpg 12mi test ride outside temp 30....58mpg .The other has all seasons....same test drive same temp 61 mpg. This one averaged 54. It also had a rattle that sounded like a loose heat shield ..I could never find....seems to have gone away...like in another post I read here.