Bosch H9DC0: life time?
 

Would like to know how long these plugs last? What's the factory spec?

Thanks!

i think these plugs are designed to be replaced at 12,000 miles as per the maintenance booklet.

If you will gap them a little tighter than factory spec at .035, you will get a better idle and you can get 30,000 before changes without any trouble as long as the engine is in good shape and running right.

Don't use the platinums. The center electrode is too thin which makes a thin spark that contributes to a bad idle. The platinum has also been known to break off and destroy engines.

Good luck,

At dealer we see these plugs going 45,000 to 60,000 miles!
30,000 is the recommended life cycle.

Larry,
What is the factory gap spec?

.035" is about 0.9 mm. Earlier in this Forum, the recommended gap mentioned was 0.04" (=1mm), claiming a bigger gap gives a bigger spark, giving a better ignition, giving a better idle.
Have my plugs now at 1mm, and engine idle's fine.

Cheers!

For '88 the recommended replacement interval is 30K miles, with a "remove and inspect" at 15K; 30K is typical for a conventional copper core plugs on an engine running unleaded fuel, but on a clean burning engine they could probably run 60K before the electodes are seriously worn.

The recommended gap is .032", which seems a bit narrow, but it will grow with use. Wider gaps generally give a smoother idle.

Duke

vronsky

i suppose on the 200e,the plugs last longer than on my 190e 1.8.

my car has h7dco plugs designed to last 12,000 miles as it is a smaller and hence a higher revving engine.

the gap specification is 0.8mm..

just a few thoughts

Yes, a longer spark would be better, but you can only make a longer spark easily in a vacuum. Inside the combustion chamber where pressure and fuel air exist, a wider gap presents greater resistance. Greater resistance makes it more difficult to create the spark. With fresh plugs, the wider gap might work okay, as they collect deposits, the wider gap will present problems.

Good luck,