Changing spark plugs advice
 

I purchased a 2011 RX 350 with 107,000 miles from the original owner . The original spark plugs have never been replaced.
My mechanic says the job is very labor intensive to replace the rear 3 spark plugs along with the front 3 plugs which are more accessible. I plan to replace the 3 rear ignition coils at the same time.
Can you recommend inspecting and/or replacing any other items that are more accessible during this repair to avoid additional expensive repair cost in the future?

The only thing I would change during the spark plug replacement would be the rear ignition coils that goes on the rear spark plugs, but they generally do not fail so it may or may not be needed. The only issue is that the rear coils will require the same amount of labor to remove in the future as the rear spark plugs if one does fail. I recommend just swapping in new coils now to avoid that issue a couple years from now after the spark plug change.

Be aware that factory Denso or NGK iridium spark plugs will easily do at least 150,000 miles before showing any electrode wear. Some folks have run their iridium plugs for more than 200,000 miles with no degradation in performance. If you are having no ignition-related issues, I would leave the factory plugs in place for now.

I would leave the spark plugs alone until you hit over 130,000 to 150,000 miles. Changing them now will not improve mileage, or running smoothness, or power and is a waste of money. Save up for when something more likely fails.
Do some more important maintenance if it has not been done, such as a coolant change, or brake fluid change or transmission drain and fill.

I agree that the plugs may not need to be changed until later, but I am not sure that it is proper to say for a fact that engine will run the same with new plugs as it is now with 100k mile plugs.

However, you got a point that a fluid change(transmission, brake, coolant) would be the better route to go on a high mileage RX.

Have almost 150k on my original plugs. Engine still runs smooth. For now, no plans to change the plugs though I did buy an OEM set of plugs recently just in case I am up for a challenge a summer weekend.

Isn't the PCV valve valve somewhere awkward back there and would make sense to replace during a spark plug swap?
*If the OP decided to swap based on the original post.

The PCV valve is on top of the engine and can be swapped in minutes once the plastic engine cover is removed.

The plugs are more labor intensive than other cars but it is not rocket science. Just watch some videos and take it step by step. Essentially, you remove the intake plenum and everything attached to it. I have heard but not done the rocker panel removal method. I would leave the coils alone. You can reach in and remove the two of them without removing the plenum. I am about to change the plugs in our 18 RX350 at 60K - it is required to maintain the emissions warranty. After 100K, I can go back to 100K plug changes.

The older 3.3 V6 have the PCV valve on the rear valve cover like on my 2007 Toyota Highlander. The 3.5 V6 PCV is easy to get to and change on the front valve cover.

The PCV valve on the rear valve cover near the firewall on the 3.3V6. A real pain to get to on that engine. It is best to change the spark plugs and coils while you are there as well on both engines. I used new rear Denso coil packs on my 3.3 V6 and will do the same on my 3.5V6 when I change the spark plugs.
https://live.staticflickr.com/65535/...125d557d_k.jpg

Agreeing with others - when the factory interval came, my local dealer recommended skipping it. He said they had replaced a few and saw no indications that they were anywhere near actually needing replacement. At 185,000, when we decided to hand the vehicle down to our kids for school commute, rather than getting rid of it, we decided it was finally time and had the replacement done. But even at that point, there were no drivability issues, and the new ones didn't seem to make any difference/improvement.

my 2c:

Recommended replacement interval is based on pre-expected failure coupled with other services. => Not a must but recommended.

When it comes to spark plug replacement, my view is it will be needed twice or thrice in the life time of the vehicle. For most CL members it will happen only once.

So do you save money by not doing the replacement? My answer is no and in fact it will cost you more as the parts + service will cost you more down the line. If you decide to sell, a savvy buyer will ask for discount on neglected [used loosely] or imminent service.

I personally would not hurry based on odd, but plan to do it fairly close to the recommend time.

Salim

I replaced my plugs last spring at 110K and they probably didn't need it after inspecting but once you're that far in, you might as well.
No regrets - it's recommended maintenance. There are several good video's that will take you through the process (that is not complicated by time consuming)

It is easy to pull and inspect all three front spark plugs. If they are still clean and show no obvious wear, it is likely that the three rear spark plugs are in similar shape. There are always exceptions, but if my front plugs are okay I am not doing a spark plug job at that time as long as there are no engine performance issues.

Very logical method. However, I do not assume anything. I would just change out old spark plugs after 100k miles or so before dealing with any misfire issues or reduced performance. However, the OEM plugs do seem to last a long time pass 100k miles without any noticeable problems; hence why I have not changed out my 2015 RX spark plugs with about 182k miles. But, I know that my engine is probably not running at its best with the 180k mile spark plugs.