Spark plugs

Not open for further replies.
May 13, 2009
Canada, SK
Is there any diffeence between Denso iriduim plug and a NGK iridium plug, or are they pretty much the same. I do perfer NGK's over other plugs that i have tried. My other question is i checked my truck plugs (8 cylinder) and have a tan color on the insulator is that normal on 30000km on a irdium plug. My previous vechicle 4 clinder i check the plugs (iridium) at 70000 km and didn't have a tan color. Should i be thinking about changing the plugs, yet or wiat until 100000 km's.
the denso iridium that comes with 0.4mm need less voltage compared to NGK, so it will help on car with weak ignition.
Lifetime wise it depends on the ground electrode, the one comes with platinum or platinum chip will last longer 100,000 km. NGK or Denso iridium for OE (comes with bigger center iridium 0.6-0.7mm) even lasts about 175,000km.

Performance wise, it depends on the gap and ground electrode shape. Theoritically Denso Iridium Power give better power due to smaller center electrode, but in certain engine the tip may overheat and produce less power compared to NGK.

The tan color on insulator as long as it is dry, should not caused concern except you find the insulator oily, that indicates gas leakage.
Spark plugs don't color like they used to with pure gas.
But your tan color is OK.
It shows the heat range was correct for the conditions immediately preceding their removal. They will change when driving conditions change, so forget about reading them as being meaningful.

Many iridium plugs only use iridium on the center electrode. The other can be plain or platinum tipped. Rarely is iridium used on both.
Is this a problem? If you have a common waste spark ignition, it can be.
Not open for further replies.