I was chasing down some plugs for my 02 TB and contacted ACDELCO.
Here's some interesting news I just got from ACDELCO concerning spark plugs for the Trailblazer. ACDELCO spark plugs 41-965 and 41-981 are being replaced by 41-103 (GM 12598004).
I am including the email I sent them and their reply. Know that this information has also been verified by calling their number at 1.800.223.3526.
My email to ACDELCO:
My vehicle is a 2002 Chevy Trailblazer. In your on-line catalog you show
two spark plugs available for my vehicle - a 41-965 and 41-981. My question
concerns the interchangeability between the two plugs. Is the 41-981
replacing the 41-965? My vehicle came with 41-965 OEM with a .043 gap,
however, you're showing a .049 gap. ACDelco previous had .043 listed for
this plug then they changed it to .049. Which is correct and why the
change? What are the operating characteristics between the two plugs - heat
range, etc? Any and all info you can give between the two plugs would be
greatly appreciated. Thanks, John.
Here is their response:
Thank you for writing ACDelco, John.
We appreciate your e-mail regarding the spark plug for your 2002 Chevrolet
TrailBlazer. Please know the 41-965 and 41-981 spark plugs have been
Be aware the 41-103 Iridium spark plug is the recommended spark plug for
your vehicle. This spark plug should not be deviated from preset gap.
We are sorry that we cannot be of more assistance with this inquiry. If
further assistance is required please call our representatives at
1-800-ACDelco (1-800-223-3526). They are available from Monday through
Friday, from 8 a.m. until 8 p.m. Eastern Time, for your convenience.
Thank you for your interest in ACDelco.
ACDelco Customer Assistance
The ACDELCO plug 41-103 is also used on the 2006 Trailblazer. The tech I talk to on the 800 number verified that both 41-965 and 41-981 are being replaced by the new plug and that production has stopped for those numbers. You can still use the previous numbers if the parts are available. I also asked if the 41-981 replaced the 41-965. The tech said yes but could not answer why the gaps had been changed for the 41-965.
*Note that info this is only for the 4.2L I6 engine.
So I guess they've answered by quest for the plug I will be installing in my TB!