So, what is it?

1.1 mm = .043 in.

or

1.3 mm = .051 in.

The owner's manual for 2007 Fit calls for NGK or Denso 1.3 mm plugs, but so many owners are gapping their out-of-box NGKs and Densos to .043 in. There are dedicated spark plug change threads here at Fit Freaks claiming that .043 is proper. Is there any indisputable evidence that would indicate one gap or the other?

Seems the L12A and L13A engines call for the 1.1 mm (.043 in.) plugs.

Spark Plug Inspection (L12A/L13A)

But if that's the case, and if the owner's manuals for the Fits with L15 engines call for the 1.3 mm (.051 in.) plugs, then what gives? This should probably be cleared up.

 

Up to you from the manual:

1.0-1.1 mm (0.039-0.043 in.)

A wider gap is better if your coilpack can handle it (most can) mine are at .045

 

Is this from the "manual" for the L12A and L13A, the service manual I linked to above?

Like I said, I've got an L15A, and my owner's manual calls for either NGKs or Densos pre-gapped at 1.3mm (part numbers ending in 13), not the ones pre-gapped at 1.1mm (part numbers ending in 11). See what I'm saying?

 

It is NOT crucial pick one the larger the better if your system is up to it. Plugs come pre-gapped now buy the ones you like and check to be sure they are all the same and install.

 

Of course, but I'm talking about a stock Fit here. Hence, the allusions toward owner's and service manuals. I should have been more clear. For a stocker, this begs for clarity and decisiveness. Depending on how you look at it, this is between a 15% and 18% variation in gap. And that's pretty huge.

Not to mention, why would I purchase the 1.1 mm plugs when the owner's manual calls for the 1.3 mm plugs? Moreover, why would anyone buy the 1.3 mm plugs only to gap them down to 1.1 mm - when meanwhile, the owner's manual still calls for 1.3 mm plugs?

Again, there's spark plug change threads on here instructing people to use a gap between .043 and .044 in. I haven't seen one yet within this forum instructing owners of L15As to use what's specified in the owner's manual (.051 in. or 1.3 mm). It's confusing, and it needs to be cleared up.

For a stock L15A, what is it?

 

Like I said use what you want it's NOT CRITICAL. Or simply go by YOUR owners manual nothing confusing about it.

 

A 15% to 18% (approximately .2 mm) difference in gap not critical? Could you explain, please?

 

WHEW all changing the gap does or not does is making the flame kernel larger or smaller. That small variant still means there will be a spark to ignite the fuel mixture.

For PERFECTION one would need to vary the gap larger and larger until the combustion "blows out" (like a birthday candle) the flame kernel then drop back a minute bit.

For a stock fit or any car one would never notice a difference of 15-18% simple if you are this particular either go by YOUR owner manual or buy a set pre-gapped and put them in.

 

Upwards of 300whp on some Fits and the stock coils were up to the task. Gap accordingly.

<100whp on a stock Fit can take a pretty fat gap without issues and is actually beneficial in some instances..

 

I guess I won't worry about it then, and just go with the OEM NGKs: 1ZFR6K-13 (.052). I still don't understand why people insist on .039 to .044, though. . . if it really doesn't matter.

 

If I remember right, and it's been a long time and with older technology so please correct me if it no longer applies--

The gap increases with time, so the gap when new and the gap after 10,000 miles are a bit different. I don't know that it much mattered when we replaced plugs every 10,000, but now with 100,000 mile plugs do they still widen out with usage?

Because if that's the case might it make sense, if you're going to regap or replace more often, to start with a wider gap because Honda picked the gap based on average over 100,000 miles?

 

I'm thinking that with electrode and ground burn, the gap could theoretically increase over time; but I'm also thinking because Honda engineers designed the L15A with 1.3 mm iridium plugs, then that's what I'm going with.