I read a while back that H9DCOs may be better than H9DCs? Any truth? Do they cost more?
Thanks.

The "0" at the end on any Bosch plug means that it will operate "better" under a wider heat range! ie; cold weather vs hot weather OR hard driving vs putting around town.
OF course they cost more.

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The local NAPA sells H9DCs for $.99 and claims they have a new number-7574. What is the number for H9DCOs? Napa only cross references by vehicles and the usual plug for 87 300E is the H9DC.
Thanks.

Did you try Fastlane? H9DC0 sells for $2.26. The last digit is a ZERO(0) not O.

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

The "O" or 0 at the end indicates a heavy duty center electrode per the Bosch catalog. Our shop uses the "O' or 0 suffix sparkplug instead of the non-O or 0 sparkplugs with good results. MB started recommending this plug beginning August of 88 for vehicles beginning at that date, we went ahead and made it retroactive to include the previous engines as well. The plug is otherwise identical, so why not have the heavy duty electrode?
Gilly

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