Wrong. The OP's .sig line indicates he has a v6 engine.

what!!!

Well, in light of differing comments here, I cracked open the Haynes Repair Manual, not entirely clear, but it may depend on the type of spark plug.

Maintenance schedule verbatim quote:

Not sure, but this seems to mean copper every 30K, while the two others mentioned above can go longer. I've seen references on the internet (so it must be true), platinum go up to 60K miles, iridium up to 120K miles.

Any thoughts on this? Thanks.

P.S. Edit to say that Haynes does not differentiate on this between the V6 and V8.

I am quoting the Toyota Factory Service Manual for a 2003 4Runner. A haynes manual means nothing compared to what the Japanese published as official OEM document. They even tell you what spark plugs to use....

Attached Images

 

I don't doubt that, but Haynes is all I had at my disposal.

Thanks for that information.

Factory replacement recommendations for 2003-2009 4Runners are 120k for Iridium Spark Plugs used in the 2UZ-FE and 30k for the Standard Resistor style plugs used in the single VVTi 1GR-FE engines. Some older Tundra and Sequoia used standard plugs, but by about 2002~2003, all 2UZ-FEs should have been specc'd for Iridiums.

You can run plugs longer, but that doesn't mean it's recommended or that they are working efficiently. I've seen people run 1GR-FE engines into the 120k range on factory plugs. But I've also seen plenty of misfire, failed coils, poor idle, intermittent issues because of that. Keep in mind that the factory gap is supposed to be something like .040", that doesn't mean that the ignition coil can't fire the plug if it's .050", but it means that the coil has to work harder and likely won't be as hot or strong as factory specification.

Thank you for this, adds much more perspective. Much appreciated.

I have a 2004 V8 and replaced my OEM plugs at 98,000 miles with iridium plugs, Denso SK20R11. I went to Advance Auto at 60,000 and was advised to wait until I was at 100,000 since they were iridium.

My owners manual says to use only iridium plugs and not to gap them.
However the specifications section says .043" is the gap.
Replacement: 60,000 miles or 72 months
V8 Denso SK20R11, NGK IFR6A11
V6 Denso K20HR-U11. NGK LFR6C11

So bad advice from Advance Auto. I'll be replacing the plugs pronto. I tow a 23' aluminum travel trailer of about 6,000 lbs. and my 17' bass boat, about 2,000 lbs. I've not had any issues with idling or acceleration. gas mileage remains the same, in town or on the highway.

I have been told that the spark will most certainly make the necessary arc to ignite the fuel mixture but idle can suffer and the engine may even stall when slowing to a stop. I've not had that experience.

Thanks for this input. Looks to me like you're doing the right thing.

From the NGK site:

"Traditional Single Iridium Plugs Denso's Iridium Power and NGK's Iridium IX series have iridium fine-wire center electrodes with tranditional nickel ground electrodes. The ground electrode will wear out first. Typically we have found you can expect 50-80k miles on a traditional iridium plug. But plug manufacturers have to temper their projections as driving conditions and motor modifications differ. Additionally, because gradual wear will "round-off" firing points over time, the concentrated firing power and voltage requirement benefits will be reduced. Therefore, NGK gives them a life expectancy of 40-50k miles and Denso assigns a recommended replacement interval of 30k miles."

Interesting, and thoroughly confusing...LOL

Totally confusing, especially since my T4R came with Denso plugs and I can't find the NGK plugs. I'll follow the manual and get the Denso plugs, change at 60,000 going forward. YMMV

Just an FYI, any manufacturer is going to "underestimate" the life of their product so they aren't held responsible for premature failure, both NGK and Denso long life versions of the iridium plugs will easily last 60,000 or more miles.

Thanks, Skip...

Not to be cynical, but could also enhance sale volumes.

I wonder why the difference in recommendations? I would imagine if Toyota thought the Iridiums couldn't last 120k, they wouldn't recommend it. i.e. the direct injection engines recommend 60k intervals on their plugs.