Which Spark Plugs and Air Filter
 

I was wondering what would be the best spark plug and air filter for my 1989 300ce?

OEM
 

OE for plugs and most probably for air filter too... The thing to remember here is that most plugs have built in resistance and our MBZs do not require that type since the wire jacket/sleeve provides 1kohm...

cheers,

Would you recommend copper or platinum?

Only copper
 

The car was engineered for copper, so I recommend you use copper plugs.

Copper
 

Use copper for sure, I have had some weird stories about plats do a search, there is a wealth of info on this topic.

Is the correct Bosch Part # H 9DC0 ?

I see 2 different part numbers.

1. H 9DC - I think this one is Bosch Super
2. H9DC0- I think this one is the OEM

Can someone please verify this?

Also, my cost on the H9DC0 is $25 Canadian or $19 US including taxes for all 6.

Is that price fair?

1. On the plate in the engine bay are specified H8DC (slightly hotter)

2. The price is fair - I paid about $20 w/ taxes for a set of 6.

~Nautilus

plugs
 

I'd stick with Cu and use the one w/o the "0". That's what I use which is perfect up to 100mi/hr as per CD. The "0" just means a larger electrode diameter.

It appears you should be using H9DC. I'm looking at the chart and H8DC should be used for "Basic and national version except AUS, J, and USA. H9DC is spec'd for Low Compression for those areas, but are for normal for ours.

cheers,

sjsfiji

I'm definitely going to get the copper. I'm wondering why you don't use the H9DC0?

In the Bosch heat range system the higher the number the hotter the plug, so 9 is hotter than 8.

The "0" suffix has a larger electrodes. Theoetically they should have longer life, but the standard electrode version has no problem lasting 30K miles. Given the additional price of the "0" suffix plug, I don't think they are worth the additional cost.

Also, I believe that the larger electrodes contribute to idle misfire, which can cause emission problems and is the likely source of the slight idle roughness that is typical of 103 engines. Since the electodes are relatively cold compared to incipient flame front temperature, they will have more tendency to quench the incipient flame and cause a misfire.

Duke

So are you saying that the "0" version may cause slight idle roughness?

It's a hunch based on my graduate training, including combustion theory, at the University of Wisconsin Engine Research Center, but I have no way to prove it.

I use the H9DC.

Duke

Sorry for asking so many questions, but I understand that you are content using the H9DC, but have you ever tried the "0" version before?

The "0" version was OE, and I bought my car new.

You're beating this to death. Just flip a coin - heads H9DC0, tails H9DC.

Or buy a set of each an run your own experiments.

Duke

I bought the H9DC and will change the plugs in the next couple of days. My supplier told me that they sell the H9DC all the time and they only had 5 H9DC0 plugs in stock and also mentioned that the last time they sold the H9DC0 was 2 years ago.