Thread: V8 plugs at 90,000

Top 4 look to be a bit on the lean side, maybe the gap is too wide, compared to the new plug, the sooty plug looks like it might not have been firing properly, probably under load, it doesn't look oily, so maybe this plug is breaking down. The correct colour should be somewhere between what you have and light biscuit brown, make sure you check and adjust the air gap on the new plugs before fitting, don't rely on them being set correctly at the factory, Regards Frank.

Lot more erosion on the sooty plug. A faulty coil? What is the other plug on the same coil like? Maybe leads?
Regards Philip A

Originally Posted by Tank

Top 4 look to be a bit on the lean side, maybe the gap is too wide, compared to the new plug, the sooty plug looks like it might not have been firing properly, probably under load, it doesn't look oily, so maybe this plug is breaking down. The correct colour should be somewhere between what you have and light biscuit brown, make sure you check and adjust the air gap on the new plugs before fitting, don't rely on them being set correctly at the factory, Regards Frank.

Agreed but if thats a genuine 90K on them and they havent been touched previously then its all looking good, definately too much gap by about say 25-50% (based on a cough comparison using the thread as a guide) but that can be accounted for by erosion of the tip and probabley running a touch lean or too hot a plug for the engine. I make it a point to change the leads when I change the plugs as if you have had breaking down of one of the leads causing a weak spark you'll get the same problem again on the same pot with the new plug. In theory though you should be able to get a set of leads to do 2 sets of plugs.

Dont go changing plug temps as your probabley going to find that the next cooler plug will be too cool and will soot up causing other problems..

The very slight sooting youre getting on a couple of the plugs might be a touch of oil getting past the inlet valves or a slight drop in compression on those pots. In any event its not bad enough at this point to worry about.

the plugs that came out were
champion RC11PYPB4---

both rears were the same colour and equally worn
5 and 6 were about the same in colour and erosion, both had that slight domed effect,,
all plugs were similar in tightness

(the leads were very hard to get off)


it did feel a bit fluffy when cold,,
much better now.

I replaced the chumps with NGK laser platinums
PFR5G-11.



at $18 each.

I'll be happy to get 90kay out of this set

Originally Posted by Pedro_The_Swift

the plugs that came out were
champion RC11PYPB4---

both rears were the same colour and equally worn
5 and 6 were about the same in colour and erosion, both had that slight domed effect,,
all plugs were similar in tightness

(the leads were very hard to get off)


it did feel a bit fluffy when cold,,
much better now.

I replaced the chumps with NGK laser platinums
PFR5G-11.



at $18 each.

I'll be happy to get 90kay out of this set

As Dave said, a new set of plug leads would be a wise investment, probably the reason the sooty plug is breaking down and sooting up, Regards Frank.

plugs are fine......

keep driving and stop looking for problems.......change the leads at the same time as the plugs and drive for another 100,000kms......

*blinks* and to think i change my plugs every 15,000km

are yours platinum......?


if they are......they are meant to last between 60 and 100 thousand kms......