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Denso (3421) SK20HR11 Iridium Long Life Spark Plug, Single Plug

by Denso
4.8 out of 5 stars 43 customer reviews
| 7 answered questions

List Price: $20.32
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  • Enter your model number above to make sure this fits.
  • Single Plug
  • Denso # 3421
  • Extra Long Life Iridium Plug
  • 0.7mm Fine Wire Iridium-Tipped Center Electrode
  • Platinum Tipped Ground Electrode
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Note: Denso partners with other manufacturers to supply the parts your car was originally built with. This product is in a Denso package, however the part may have been manufactured by an independent Denso supplier.
$6.80 Add-on Item & FREE Shipping on orders over $35. Details Only 1 left in stock. Sold by Peace Tree and Fulfilled by Amazon. Gift-wrap available.

Frequently Bought Together

  • Denso (3421) SK20HR11 Iridium Long Life Spark Plug, Single Plug
  • +
  • Permatex 81343 Anti-Seize Lubricant, 1 oz. Tube
  • +
  • Permatex 22058 Dielectric Tune-Up Grease, 3 oz. Tube
Total price: $17.08
Buy the selected items together


Product Information

Technical Details

Brand Denso
Item Weight 2.1 ounces
Product Dimensions 3.6 x 1 x 1 inches
Item model number SK20HR11
Manufacturer Part Number 3421
OEM Part Number 3421

Additional Information

ASIN B002FOO884
Customer Reviews
4.8 out of 5 stars 43 customer reviews

4.8 out of 5 stars
Best Sellers Rank #22,227 in Automotive (See top 100)
#68 in Automotive > Performance Parts & Accessories > Ignition & Electrical > Spark Plugs & Wires > Spark Plugs
#167 in Automotive > Replacement Parts > Ignition Parts > Spark Plugs & Wires > Spark Plugs
Shipping Weight 8 ounces (View shipping rates and policies)
Domestic Shipping Currently, item can be shipped only within the U.S. and to APO/FPO addresses. For APO/FPO shipments, please check with the manufacturer regarding warranty and support issues.
International Shipping This item is not eligible for international shipping. Learn More
Date First Available January 1, 2007

Warranty & Support

Warranty, Parts:PartsWarranty, Labor:Denso honors the manufacturer's warranties for the products purchased from Denso. Please note that shipping charges for all warranty items are the responsibility of the customer. Parts that are damaged due to incorrect installation or mistreatment are not covered under warranty. Denso does not express or imply any warranty as to the performance of any part sold. Denso is not liable for damages of any kind arising from incorrect part application. Denso is not liable for the use of parts purchased on this site, including but not limited to punitive, indirect, direct, incidental, and consequential damages.

Product Description

Iridium plugs have an extremely long life as Iridium is 6x harder and 8x stronger than platinum. Because of the strength and hardness of iridium, there is virtually no electrode wear. This combined with a platinum tipped ground electrode, creates a spark plug that is almost impervious to wear even under extreme driving or racing conditions.

Customer Reviews

Top Customer Reviews

Verified Purchase
My last set of these lasted 100,000 miles. They didn't really look worn when I took them out. I only replaced them due to being in the engine for 100,000 miles. This plug is an exact replacement for my Toyota 4 Runner. The engine is a 1 GR FE V 6 engine.
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The Denso SK20HR11(Gap-.044") is the original plug that came stock on my Toyota 2TR-FE engine so I used the same ones when replacing, can't go wrong with these.
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Verified Purchase
My FJ Crusier 2007 had all the dash lights turn on. Checked the fj manual, and all said to take it to a dealer. Instead, took it to an auto shop (shuck's) and got the computer read out. The codes said, I might have an issue with the cadillac converter. Casher said, it's almost never the convertor, try new spark plugs.

Bought these sp's and installed myself. Gapping for fj should be 0.38-0.43. These come at 0.44. I didn't make an adjustment. Installed watching a Youtube video. Took about 2 hours. Make sure you purchase a 3/8 inch ratchet with a torque measurement ($40) in/lb, 3/8 - 1/4" ratchet convertor, spark plug bit with magnetic bit (must) and correct lube.

After installation, turned off all dash lights. Car now runs at fj standard 550 rpm (was at 1000 rpm). Saved a ton of cash doing this myself. The sp's were brownish at the ends when I took them out. I will now swap out every 30k (recommended). Should only take an hour now.
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Verified Purchase
The plugs came pre-gapped which save time during install.

Would buy this product again (and will for my Subaru STi).
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Verified Purchase
These are the original equipment for my 2006 Toyota Tacoma pickup truck with the 2.7 liter 4-cylinder engine. I installed a new set of these plugs when the truck had just over 100,000 miles. They work great and have been very reliable. I am very confident this new set will work perfectly for the next 100,000 miles.
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Verified Purchase
Worked as expected on my '07 Tundra. They came pre-gapped correctly and installed just fine. I replaced all the plugs at 100k miles and after a few thousand miles, I haven't had any issues. I may pull them in a few thousand more to see how they're holding up; I'll provide updated feedback then.
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Verified Purchase
I replaced my plugs for the first time with these @ 123K miles as a proactive maintenance measure as my FJ was running just fine. I can't say that my truck is running any better but it's definitely not running worse so I would say that at the very least these are the perfect replacement for the OEM plugs. NOTE: the OEM plugs I took out were also DENSO, just not the iridium. I expect the iridium long-life plugs will perform even longer but we'll see ... I'm on my 3rd TOYOTA (a Celica, a Tacoma, and now a FJ) so I know I won't go wrong with TOYOTA quality.
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By MB on December 19, 2015
Verified Purchase
These are exactly the same factory installed plugs on my Tundra v8 5.7 2010. It took me about 90mn to replace all 8 plugs. Old plugs were dirty coming out though did not look worn out or damaged after 100k miles. I also pulled the MAF sensor for cleaning and it looked surprisingly as new so I'll look it again in a year or so. Truck has been running about 14 mpg this past year and it was closer to 14.8mpg first 50k miles. Hope the new plugs will help a little bit...
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Want to discover more products? Check out these pages to see more: iridium plugs for lancer, fj60 parts, bmw e30 performance parts, subaru impreza outback sport, fj40 land cruiser parts

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Denso (3421) SK20HR11 Iridium Long Life Spark Plug, Single Plug
This item: Denso (3421) SK20HR11 Iridium Long Life Spark Plug, Single Plug
Price: $6.82
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