[bassman29]

Hello
For the last two services at my dealer they have suggested replacing my spark plugs on my 2017 4runner with 95k miles. I am confused because the service manual states that they are due for service at 120k. First tech did not say much the second tech said that Iridium plugs only last 100k. Which one is it 100k or 120K


Thx
Peter

[Bmnorm2]

Both answers are correct. Generally iridium is rated for ~100k miles. Toyota recommends 120k, which is acceptable too.

If you aren’t experiencing any spark related issues then have them changed at some point between 100k and 120k miles.

[DougR]

I replaced spark plugs at 120,000 miles after 11 years in service. I had no engine codes and no issues before or afterwards. The plugs were tight, so I alternated between counter-clockwise and clockwise rotation. If I were you, I'd wait until 120,000 miles.

[HEAVY WT]

120k. Toyota wouldn't recommend an interval of 120k if the product was only for 100k. FYI I'm at 126k and should be getting around to changing my out soon. Still runs fine. When I changed my S2000 at 100k they looked pretty clean still (iridium also). Granted based on the oil change debate, there will be people here who say every 50k to be "safe" lol

[///AIRDAM]

They will last well into the 150K+ range, normally see them burning out around 190,000-200,000 but have seen / heard of instances where people didnt replace them until one burnt out around 250,000

drivers side, normally the middle or rear cylinder is always the one that shows the most wear on the electrode. Cant confirm why, but they will typically go well over 100K miles.

[thatoneguy]

Originally Posted by ///AIRDAM

They will last well into the 150K+ range, normally see them burning out around 190,000-200,000 but have seen / heard of instances where people didnt replace them until one burnt out around 250,000

drivers side, normally the middle or rear cylinder is always the one that shows the most wear on the electrode. Cant confirm why, but they will typically go well over 100K miles.

Spark plugs can often go a really long time. My '99 4Runner was on 210,000 miles when I sold it on the original spark plugs, and those things used a wasted spark system.

[Ezlife45]

I went to change plugs on my V-6 honda accord at 100K and when I pulled them they looked brand new. I reinstalled them and ran another 100K before doing anything with them.

[1000MPH]

I first replaced mine at 6 years and 81,000 mi. They weren’t hard to remove but there was a lot more resistance than I was comfortable with in an aluminum head. I pulled them because I just wanted to check condition, and try my new wrench. I found a lot of deposits on the ground electrodes and gap was way off. I replaced them rather than clean and regap. This month I checked them again and decided to replace them again (135k). Same issue, a lot of deposits and gap out of spec. Maybe it’s that California gas?

[flyrv9]

Nice write up by Antman in the stickys on how to change plugs on a 5th Gen.

[DougR]

Originally Posted by 1000MPH

I first replaced mine at 6 years and 81,000 mi. They weren’t hard to remove but there was a lot more resistance than I was comfortable with in an aluminum head. I pulled them because I just wanted to check condition, and try my new wrench. I found a lot of deposits on the ground electrodes and gap was way off. I replaced them rather than clean and regap. This month I checked them again and decided to replace them again (135k). Same issue, a lot of deposits and gap out of spec. Maybe it’s that California gas?

I kept my 120,000 mile spark plugs and labeled them with the bank and cylinder for comparison on the next change at 240,000 miles. Overall, mine are cleaner than the one you show. The worst of them is about the same except all plug grounds have less deposits. Phoenix has a special gasoline blend to reduce air pollution (which increases our fuel cost). The gap on my plugs is typically 0.001 inch over spec when measured with pin gauges. I don't know why the gap on your plugs increased.

[Charles Bronson]

Plugs can last as long as Toyota notes, but my concern is the duration of time the plugs are in the head. Carbon and other various types of build up occur on the plug tip and about usually about part way up the threads. This can make plug removal difficult.

As others noted, one must be very careful when removing aged plugs. If you feel resistance when removing, tighten them back up a bit, and then start loosening again. This will help break down the build up in the threads and reduce the potential of cross-threading. Be patient and take your time.

I plan to break the plugs loose on my wife's 2020 4runner this winter (50K miles) to inspect the plugs and to free them up so that they are easier to remove when they need replacing in a few years.