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The first-generation Lexus RX300 (1999-2003) runs the 1MZ-FE 3.0L V6, an engine with a well-documented factory-correct plug — Denso’s SK20R11 is the OEM part sold under both Denso and Toyota/Lexus part numbers. These eight real, verified options span iridium, twin-tip, and platinum tiers, and the rear bank’s location makes labor, not the plug itself, the real cost driver on this job (see the tips).
| # | Product | Price | Where to buy |
|---|---|---|---|
| 1 | Denso SK20R11 Iridium Long-Life | $30-$62 for 6 | Amazon · eBay |
| 2 | NGK Iridium IX (BKR6EIX-11) | ~$52.54 for 6 | Amazon |
| 3 | NGK Laser Iridium (IFR6T11) | ~$60-$90 for 6 | Amazon · eBay |
| 4 | Denso Platinum TT (PK20TT) | $7.25-$12.50/plug ($44-$75 for 6) | Amazon · eBay |
| 5 | NGK G-Power Platinum | $35-$60 for 6 | Amazon · eBay |
| 6 | Autolite Double Platinum (AP3923) | ~$8.29/plug (~$50 for 6) | Amazon |
| 7 | Bosch Double Platinum | ~$6.69/plug (~$40 for 6) | Amazon · eBay |
| 8 | Champion Iridium (RC9WMPB4) | ~$6.80/plug (~$41 for 6) | Amazon · eBay |
The picks, in detail
Denso SK20R11 Iridium Long-Life
The genuine OEM plug for the 1MZ-FE, sold under Denso’s own catalog number (3297) and the identical Toyota/Lexus OEM part number 90919-01210.
- OEM part for the 1MZ-FE, cross-references to Toyota 90919-01210
- Iridium fine-wire tip
- Rated up to 90,000-mile service life
- The exact factory plug — zero fitment guesswork
- Owners in RX/Lexus forums consistently return to this part after trying alternatives
- Priced higher per plug than basic platinum alternatives
NGK Iridium IX (BKR6EIX-11)
NGK’s Iridium IX line, sold with explicit fitment for the 1999-2003 RX300 base 3.0L V6 — a well-regarded aftermarket alternative to the Denso OEM part.
- Iridium fine-wire center electrode
- Explicit fitment listing for 1999-2003 RX300 3.0L V6
- NGK’s mid-tier iridium line
- Confirmed RX300-specific fitment, not a generic cross-reference
- Trusted NGK iridium quality
- Priced above basic platinum options
NGK Laser Iridium (IFR6T11)
NGK’s premium iridium tier, also sold with explicit fitment for the 1999-2003 RX300 base 3.0L V6, a step up from the standard Iridium IX line.
- Premium laser-welded iridium tip
- Explicit fitment listing for 1999-2003 RX300 3.0L V6
- NGK’s top-tier iridium chemistry
- Confirmed RX300-specific fitment
- Longer rated service interval than Iridium IX
- Priced above NGK’s own Iridium IX line for the same car
Denso Platinum TT (PK20TT)
Denso’s twin-tip platinum plug, a distinct product tier from the SK20R11 iridium OEM part — a mid-tier alternative if you want Denso’s twin-tip design without paying full iridium pricing.
- Twin-Tip platinum design (iridium center, platinum ground)
- Denso catalog number 4504
- Reduced spark quenching versus single-tip platinum
- A genuinely different Denso product line, not the SK20R11 relabeled
- Twin-tip design outperforms basic single-tip platinum
- Priced above basic Bosch/Autolite platinum, below the full iridium options
NGK G-Power Platinum
NGK’s single-platinum-tip line for the RX300, positioned by reviewers as the best economical single-platinum option if you don’t want to pay iridium prices.
- Single fine-wire platinum center electrode
- Compatible with 1999-2003 RX300 3.0L V6
- Budget-tier NGK plug line
- One of the most affordable real options on this list
- Fine-wire platinum still outperforms a basic copper plug
- Shorter service life than any of the iridium options above
Autolite Double Platinum (AP3923)
A double-platinum plug sold specifically for the 2003 RX300 3.0L V6, one of the most affordable options here from a mainstream US spark plug brand.
- Double platinum electrode design
- Specific listing for 2003 RX300 3.0L V6
- Sold individually
- Confirmed RX300-specific fitment at a low price point
- Double-platinum design outlasts basic single-platinum plugs
- Still platinum, not iridium — shorter service life than the Denso/NGK iridium options
Bosch Double Platinum
Bosch’s double-platinum plug sold for the RX300, the cheapest option on this list and a common budget-to-mid alternative to Denso and NGK.
- Double platinum electrode design
- Fitment listing for RX300
- Sold individually or as a set
- Lowest price point of the verified options here
- Double-platinum design rated for roughly 2x the life of basic copper plugs
- Still platinum, not iridium — Denso’s OEM iridium part outlasts it
Champion Iridium (RC9WMPB4)
Champion’s iridium-tipped plug, cross-referenced for the RX300 in major parts catalogs (PartsGeek/AutoZone), from a long-running mainstream spark plug brand.
- Fine-wire iridium center electrode with platinum ground electrode
- Cross-referenced for RX300 fitment
- Sharp spark focus per Champion’s own positioning
- A genuine iridium option from a brand other than Denso/NGK
- Reasonably priced for an iridium plug
- Sold in cartons of 4 by some retailers — check you’re buying enough for a full 6-plug set
Buying tips
- The 1MZ-FE is a V6, so the RX300 takes 6 spark plugs — confirm any listing is priced and packaged as a full 6-plug set.
- The Denso SK20R11 is the factory-correct OEM part; if you want the simplest, lowest-risk choice, that’s it — the NGK, Denso Platinum TT, and platinum options are legitimate alternatives, not upgrades over it.
- The 1MZ-FE’s rear bank sits buried under the intake plenum on this transverse V6 — pulling the plenum to reach it is most of the labor time on this job, whether you DIY it or pay a shop. That labor cost is the real argument for fitting a long-life plug (Denso SK20R11, NGK Laser Iridium) instead of a cheap platinum plug you’ll be back in there to replace sooner.
- Don’t gap iridium plugs like the Denso SK20R11 by hand — they come pre-set, and bending the fine-wire tip can damage it.
- We could not confirm NGK’s PFR5N-11 Laser Platinum as correct for the RX300 — it cross-references to Denso’s 4503/PK16TT/IK16TT family, a different heat-range tier than the RX300’s confirmed Denso SK20R11/PK20TT ’20’ family, so we left it off this list rather than risk a wrong-heat-range recommendation.
As an Amazon Associate and eBay Partner, toptenpick.com earns from qualifying purchases. Prices and availability are subject to change.