Alright, after a little more web searching, checking my owner's manual (duh), and a call to DCH Lexus, I have learned that the double ground electrode spark plugs stopped being a necessity from 2001 on for the GS300. The '04 comes with an iridium tipped plug and platinum ground electrode, like the Denso SK16R-P11's or the NGK 4589's. The NGK's I listed earlier were platinum tipped center wire/electrode, which are a step down.

So my last question remains , would anyone recommend replacing the COP boots as well? Since I'm having them shipped, I'd rather not have to pay to ship them back if I don't need them.

 

If you're going to do all of it then do the boots while you're at it. I did.

 

Hey, good info, but could you please state why the Lexus people said it wasn't a necessity after 01, even though it's the same engine from 98. What changed from 00 to 01? Thanks. I plan on purchasing the denso plugs you listed above once I'm ready to change out.

 

gittert - Thanks, I'll definitely buy the boots, (Advance Auto's $50 off $100 definitely makes the price for these sting a little less), but might not change them if the old ones look okay.

Gogku - I just asked the service guy what plugs were OEM for the '04 GS300 and he told me exactly what all the parts search engine's and the manual saying. I asked about the double ground electrode plugs and he said that was for older GS300's. I didn't think to ask why there was a change, I guess I just assumed they tweaked the engine every few years.

I also went to the Lexus website and searched through the pdfs of the owner's manuals. Below is a list of plugs Lexus recommends for the GS300, based on production year:

1998
DENSO - PK16TR11
NGK - BKR5EKPB11
(Note: Manual specifically states to use only twin ground electrode plugs. Has a picture showing the plug.)

1999
DENSO - PK16TR11
NGK - BKR5EKPB11
(Note: Manual specifically states to use only twin ground electrode plugs. Has a picture showing the plug.)

2000
DENSO - PK16TR11
NGK - BKR5EKPB11
(Note: Manual specifically states to use only twin ground electrode plugs. Has a picture showing the plug.)

2001
DENSO - SK16R–P11
(Note: Manual specifically states to use iridium tipped plugs. Here is where the change starts, also shows a pic where it's no longer a twin ground electrode.)

2002
DENSO - SK16R–P11
(Note: Manual specifically states to use iridium tipped plugs.)

2003
DENSO - SK16R–P11
(Note: Manual specifically states to use iridium tipped plugs. There are two manuals, one for production through Apr '03 and one for production through May '03. I checked both pdfs and the plug is same.)

2004
DENSO - SK16R–P11
(Note: Manual specifically states to use iridium tipped plugs.)

2005
DENSO - SK16R–P11
(Note: Manual specifically states to use iridium tipped plugs.)

2006
DENSO - FK20HBR11
NGK - ILFR6D11T
(Note: Manual specifically states to use iridium tipped plugs. Looks like another change here, the pic looks like a triple ground electrode plug.)

Hope this helps.

 

Damn!!! You are completely correct! I just went to verify it online and it does change at 01 from twin ground to iridium tipped plugs. Well I this makes things a little easier sourcing iridium plugs from rock auto for a good price vs. trying to find the old denso plugs. I wonder what changed in the engine? I'm going to try to find that out.

 

Hey, anybody that bought spark plug wires, did they come with the snap on connectors that disintegrate when removed from the coil pack? If so, what brand/part# did you buy? Thanks!

 

Mine did. I bought NGK

 

Thanks gittert!

 

I just bought a 2001 Silver 300 that had 145,200 miles on it. Now has 147,700 miles, and I finally know what type of Spark Plugs I have to actually buy. Now the wires is whats confusing me, I have to buy 3 wires and the other COP wires separately? then buy 6 boots? Can anyone assist me? Thanks.

 

Okay, I finally now understand the ignition wires that I was confused about. Three wires will come in a set, then I have to buy 3 Coil on Pack boots. And maybe some new clips I heard will break off easy. I forgot it was wasted spark, Thanks for the help guys.