Hey guys. Got around to changing out my plugs on Monday. They all look OK, but when comparing them to eachother, they get increasingly red tinge as I go to the front of the vehicle.

Here is an image of the difference between the cylinder nearest the transmission next to the one near the radiator. Does this difference mean anything to anyone?


'99 4.0L with 139,000 km (~87000 miles).

 

Just as a clarification, they got increasingly more red as I go to the front.

These are the extremes, but it was incremental.

 

Those are some pretty clean plugs, for being 16 years old. Gap looks huge tho...

 

Here's a pic showing three basic conditions. By appearance, your red plug looks like it is running a tad lean....but:


That red splash is probably because the plug is facing the exhaust valve and may just be clocked that way by chance. The white plug looks like it's not clocked to the exhaust valve - the ground electrode is masking the splash - ideal clock.


Race car drivers are concerned about this sort of thing but I don't think you have anything to worry about.


Google 'clocking spark plugs' and see what you come up with.


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What brand and number are these plugs? They look like Champion RC12ECC plugs.