[T77911S]

that plug looks bad! looks like you have been driving in a lot of city traffic were you are on the idle circuit mostly, if not, you may want to check mixture/timing or maybe even try a hotter plug. like richf said, bosch supers are the way to go. i have not heard how well the iridium plugs do.
do a search on reading spark plugs. there is a lot to learn out there.

here is some of what i have pulled off the net. some contradicts itself, such as timing. some say read the center electrode, some say the ground strap. some of this may repaet, i copied sections from different sites. i was having a detonation problem, so i started researching plugs, timing and miture. turned out my CAMS were advanced 15deg. by PO.

Try to use a too-cold spark plug and you very likely will have to jet for a lean mixture to avoid plug fouling - and as you lean an engine's air/fuel mixture down near the roughly-14.5:1 chemically-correct level it becomes extremely detonation-prone. Excessive spark advance is even worse in its ability to produce detonation, and when combined with a lean mixture it's enough to quickly destroy an engine.


a slightly lean mixture detonates at a lower temperature It's all a function of ignition timing and mixture in any given engine, and spark plug heat range plays absolutely no part in it.

It's impossible to separate the question of ignition advance from the primary evidence of spark plug overheating, which is most strongly shown on the plug's center electrode. If you inspect this electrode's tip with a magnifying glass and see that its edges are being rounded by erosion, or melting, then you know there's overheating. You should also have a close look at the tip of the ground electrode, checking for the same symptoms. Finally, inspect the condition of the insulator, which should be white but with a surface texture about like it was when new; a porous, grainy appearance is evidence of overheating. If the signs of overheating are confined mostly to the center electrode you can bet you're using too much ignition advance. Retard the spark timing in small (two or three degrees) increments and as you get close to the optimum advance you'll find two things happening: first, the whole plug will be running colder; second, the center electrode will begin to acquire a film of fuel deposits extending out from the insulator nose toward its tip.


when you have found plugs of a heat range that will keep that insulator nice and clean you can start adjusting your engine's air/fuel mixture

If you think about it you'll realize that the only color you can get from an air/fuel mixture is the color of soot. When the mixture trapped in an engine's combustion chamber has more fuel than can be burned with the available air, then combustion will be incomplete and the excess fuel will remain as soot, which is not brown or tan or magenta or any color other than black. And if your engine's mixture is too rich, the sooty evidence will be present on the spark plug's insulator, in a very particular area

best performance is achieved when the mixture contains only enough excess fuel to make just a wisp of a "mixture ring" on the plug insulator

excessive spark lead is the most frequent cause of detonation, which is a real engine killer. You can't stop advance-produced detonation with a cold spark plug, nor with anything but a wildly over-rich mixture


Rich air/fuel mixtures cause tip temperature to drop, causing fouling and poor driveability
Lean air/fuel mixtures cause plug tip and cylinder temperature to increase, resulting in pre-ignition, detonation, and possibly serious spark plug and engine damage
It is important to read spark plugs many times during the tuning process to achieve the optimum air/ fuel mixture

Advancing ignition timing by 10° causes tip temperature to increase by approx. 70°-100° C