Hi,

I replaced the NGK iridium plugs on a 2003 Mazda 6i 2.3 after 60k miles. The plugs were on the engine from 90k miles to 149k miles.

What do you guys think the conditions are? See any problems?

 

The engine looks like its burning a proper a/f and no sign of detonation. So they look good overall there. Im seeing a little bit of oil contamination on the tips of two plugs and some on the threads on 3 of them. Does the car go through any oil? Any top offs between changes? The oil on the threads could just be leaking spark plug tube seals.

 

No significant sign of any oils burning. Never had to top off the oil between changes. The MPG has dropped from 29 to 26 recently but I been contributing that to the new set of tires. The new tires have a tread wear of 600 vs the 700-800 that was on it before.

 

The gap on those plugs looks a bit wide. This may have caused the mileage issue. You put new plugs into the car?

 

The plugs were replaced with the same model NGK iridiums that are pre-gapped. The gaps were in tolerance. The mpg is still at 26 instead of 29 mpg prior to spark plug/ngk wire/tire change.