I have a 2012 4cyl Honda Accord with PZEV emission standard. I had my Honda Dealer service department replace my spark plugs and I asked for the originals so that I could examine them. They put the removed plugs in the Red Honda OEM boxes that contained the replacement plugs. The Honda box shows two PNs: 12290-R41-L01 and DILZKR7A11GS . I think the first number is the Honda PN and the second number is the NGK PN.

I took the old plugs out of the boxes to examine them and they appeared to be in very good condition (no signs of fouling or electrode deterioration) but I noticed that the number in the white ceramic portion of the plugs had a very slightly different NKG part number: DILZKR7B11GS. This was a first time replacement of the plugs and the originals have a B and the replacements have an A in the part number.

The new replacement plugs (A) installed in the engine match the recommended plug according to my 2012 owner's manual. So the (B) plugs were what Honda used when the engine was manufactured for the new car.

Can anyone explain why the NKG part numbers have this slight difference. The only thing I can think of is the B is used to denote that the plug was the original plug and not a replacement plug. This might be important since plugs can last a very long time.

Thanks,

Jack

 

Google found a site that decodes NGK spark plug numbers, but your spark plug numbers didn't exactly fit the chart. This may be an older table before your spark plug was created. The spot for the A/B lists both A and B as special design. Maybe the B had some special design for Honda's manufacturing process?

Ebay showed both spark plugs numbers are interchangeable, so I wouldn't worry too much. The difference has to be insignificant.