kaze10

Okay, so I asked my service dept. tech about plugs and he said do nothing until 120k or so. I know having good plugs will provide the best MPGs. I emailed the manufacturer of both Denso and NGK and here's what I got back.

Denso (OEM)

A. Iridium use represents the most significant technological advance in automotive spark plug manufacturing, since platinum was introduced in the early eighties. As vehicle manufacturers produce increasingly complex and efficient automobiles, there is a greater need for long-life plugs that can tolerate leaner fuel mixtures and improved combustion processes. DENSO has responded to this need by developing its Iridium alloy, originally for OE applications. For example, many newer Lexus? and Toyota models carry an ultra long-life Iridium plug variation (.7mm with platinum tipped ground) that is capable of up to 120,000 miles of service. DENSO Iridium Power plugs, with their .4mm center electrode, have been developed for performance applications. Because gradual wear will ?round-off? firing points over time, the concentrated firing power and voltage requirement benefits will be reduced. For this reason, DENSO advises replacement after 30,000 miles.

NGK
These two plugs perform similarly Iridum IX and Iridum Laser Series, due to their fine wire tip design, but the service interval is different; the Laser Series are typically designed to last 80 to100 thousand miles, whereas the Iridium IX spark plugs are designed to last 40 to 50 thousand miles.

Has anyone changed out their plugs? What's you opinion on this?

TheAirman

Here's from the manual:

Owner's Manual.pdf

I haven't done mine, but usually iridium plugs last a long time. I wonder how the stop and start engine affects them over the long run, though. Does it make them wear faster or last longer?

kaze10

So, I replaced my plugs and the engine seems a lot “happier”now. When the ICE starts, its smoother. I could feel before when the engine would start and stop. I’ve picked up a few more mpgs without changing my driving style. I’m at 50k now and I was surprised at how the plugs looked. “To each his own” but if your car is over 50k I’d have them looked at or replaced.

TheAirman

Great !! Thanks for sharing.

From the picture, they don't "look" that bad. Nothing that I would ever say would make a difference in how the car ran.

So it did seem to start a little smoother? And a little better mileage?

I might pull one or two of mine to take a look.