Standard vs. Optional & NGK vs. Denso

[Spike]

I started this as a reply to an older thread, then realized that thread was under 3rd generation & I didn't want to limit the responses I would get.

OK for my 2004, in the service manual it says for replacement plugs:

Standard IMR9B-9H (NGK) or VNH27Z (Denso)
Optional IMR8B-9H (NGK) or VNH24Z (Denso)

Anyone know why you would go with the "optional" over the standard? It doesn't say. Also, any input as to why choose the NGK over the Denso? Pretty big price gap, we got, and I haven't searched for the best deal, but for comparison's sake, from the same website, $16.49 for both the NGK's and $21.59 & $29.29 for the Denso's.

Really hope this isn't like the oil thread....

On the NGK plugs, the difference is heat range, but I'm sitting in my truck in CT and I don't remember which is the hotterof the 2.

I think NGK's web site explains the alpha-numeric breakdown for plugs.



Rex

[masonv45]

Correct, heat range for riding at high-altitudes.

[Spike]

So which one is which? I assume the optional ones would be the high altitude ones? But, why wouldn't they just say that in the manual? "for primarily riding conditions above xxx feet/meters, use this one.

[masonv45]

Beats me...why does Honda call Blinkers "Winkers"???

[Spike]

The difference is the heat range, at least on the Densos, finally got an answer. Couldn't get it from Denso USA, had to go to Denso world. According to Denso US, there is no such thing as a VNH24Z or VNH27Z. Nice! Nor do they list the VFR after the 2003??!?!?

as to what the difference in the heat range means...
(copied and pasted from Denso)
Q. Why are there different heat ranges? Which one should I use?
A. Part of your spark plug’s responsibilities, in addition to firing a spark, is to remove heat from the combustion chamber. This is accomplished by channeling the heat through the insulator material and metal housing. From there, the heat is transferred to the cylinder head where the engine cooling system can go to work. A spark plug’s heat range is its ability to dissipate heat. The “colder” the plug, the more heat it can channel out of the combustion chamber. In a performance application, colder heat ranges may be necessary to handle the extreme temperatures brought on by higher compression ratios, forced induction, and high RPM’s. While “Colder” plugs may seem to be the way to go, please remember that the spark plug must achieve its “self-cleaning” temperature where it can burn off fuel and carbon deposits. Otherwise, the plug could “foul out” where it is prone to misfiring and poor acceleration. A plug that is too “hot” can overheat, also causing power loss, detonation, pre-ignition, and possible engine damage. A good, general rule of thumb is to start with the factory recommended heat range. For every 75 to 100 hp you add to your engine, you may go to the next colder step. DENSO heat ranges move up as they get colder; 16 would be our hottest Iridium Power plug, 34 would be our coldest (ranges; 16,20,22,24,27,31,34)

[nozzle]

NGK is easier to pronounce.



and spell correctly.