The maintenance schedule of my (European) RX400h calls for replacement at 90,000 Km (about 56k miles).
Now, aside from the fact that it sounds very precautionary in absolute terms, I found on the web the Canadian maintenance schedule.
And according to it, plugs should be changed at 192,000 Km (about 120k miles).
I can't for the life of me see any reasons why in Europe the plugs should last less than half compared to Canada.
My funny feeling is that the EU schedule is just made to grant some income to dealers, considering how hard it is to change the rear bank plugs...
What do you think? Thanks in advance!

PS: I'm not posting this in the hybrid section because I believe that it applies also to the 330, which has the same engine.

 

I would go by the recommendations of the manufacturer of the the spark plug. Some higher-end iridium plugs may recommend (as an example) 100,000 miles or 160,000 km, I would replace them at 80,000 miles or at 80% of the recommended millage.
Pull a plug out, check it visually & if the vehicle is consuming more fuel than usual, misfires, rough idle, stalls or more difficult to start, it would definitely be time. Wouldn't hurt to check & replace the engine coil as well.
Spark Plugs are not that expensive & a not a so difficult DIY project if "Patience" is your middle name.
Excellent video here:

 

Great video. Thanks for posting that. I have heard to NOT use antisieze on the plugs, as they already have a coating on them from the manufacturer. Anyone who has done this care to comment?

 

Have never used antisieze on plugs ever. I've never had an issue taking plugs out that were torqued to spec upon install, even plugs that came out at around 100K miles. But I typically try to change my Denso or NGK Iridiums around 80K. Just did all 6 on my RX330 a month ago, fun job......

 

Years ago the antiseize would have been great, probably not vital to have these days...
I was fortunate, the plugs & engine coil were replaced 10k miles ago by the previous owner, found an invoice in glove box of the RX330 at the time of purchase to confirm that.
A whopping invoice for $2000. (Ouch!) for the above & new calipers in the rear with some other related brake work.

 

If I am having misfires at 100k miles, I'll change the plugs out early, otherwise I will change them at 120k miles. I'm not too concerned about it.

 

LOL, I'm afraid it isn't!
Thanks for the video anyway, and for your suggestions - as well as to the other contributors, of course.
What you are all saying is pretty much what I expected/hoped to hear, i.e. that the 56k miles of EU maintenance schedule is silly.
Also because (I forgot to mention earlier) the engine runs smooth as silk, burns no oil at all, and never had misfiring or any other irregularities.
Bottom line, one less thing to worry about for another 30k miles or so!

 

Actually if Platinum Spark Plugs are currently installed in your RX330 the 56K miles would make sense, as manufacturers of this type of Spark Plug recommend 60,000 miles.
Maybe something you should look into as the front Spark Plugs are easier to get to, to verify the type they are & to also inspect the general condition visually.
My bad, should have mentioned this before in my original post.

 

Actually, the 90,000 km (56k miles) maintenance schedule specifically mentions replacement of iridium plugs, so I would hope that's what they fitted also as original installation.
Good point anyway, thanks again. My patience is probably enough (just!) to pull the front plugs and check them out.
Will do on the first occasion and report back, just in case anyone else in EU might be interested.

 

Excellent ambitious plan, looking forward to you posting your findings....
here's another video, practically a bible for analyzing spark plugs.

 

Thanks very much for the video. I suspect this is in my future soon.
A quick tip worth sharing is to put a long enough piece of straight tubing or hose on a new spark plug when first installing it (instead of using a socket to start the plug).
Turning on the tubing to first thread the plug into the engine block is much less likely to cross thread because there's more feedback thru the tubing (and the tubing is likely to turn and maybe even twist off before serious cross threading can occur).
This can be used to start the plug, or to get the plug 'finger tight' into the block. Then pull the tubing straight off, and use the socket to tighten.
Thanks again!

 

You will find the iridium plug is unbelievably reliable. Some have over 250k miles with no issues. I have three that have 196k miles and are fine. (I do plan to change them)...

 

^ ok now I am in no rush to change my sparkys.

 

Thank you for the video.
Will be doing mine soon.
Any tips on the rear valve cover gasket?
It looks like there is alot of space there to remove the rear valve cover.
Should I remove anything else?

 

Glad my video helped.

As for the rear valve cover gasket, please see my valve cover video for the 3.0L motor, which is similar: