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DENSO Iridium Power Spark Plug: Maximum Spark Energy, 0.4mm Iridium Tip, IK16

(369 reviews)
Part # 5303
1 year warranty
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Product Information

Product Details
Part No. 5303
Warranty Details (1 Year Warranty)
The Iridium Power Spark Plug is engineered for the most demanding automotive enthusiasts, delivering no-compromise performance and reliability. Featuring a patented U-groove ground electrode design, it ensures efficient ignition even with leaner fuel mixtures, outperforming conventional plugs. Its iridium center electrode tip offers exceptional durability, withstanding extreme temperatures exceeding 4000 Deg F and lasting twice as long as standard plugs. Precision machine-rolled threads minimize the risk of seizing or cross-threading, making it ideal for delicate aluminum heads. With a flat seat type and a wide range of part numbers, this spark plug is compatible with thousands of applications, including classic and collector cars. Whether you're on the track or the road, this top-of-the-line spark plug delivers unmatched performance and longevity, making it a valuable upgrade for any serious driver.

Product Features:
  • World's smallest Iridium Center Electrode (0.4mm) for improved spark for maximum combustion
  • Patented 360-degree laser welding assembly process
  • U-groove and taper cut ground electrode to maximize flame propagation.
  • Withstands temperatures greater than 4000 degree Fahrenheit
  • Burnished nickel plating for high temperature endurance and superior corrosion resistance
  • Wide range of part numbers for thousands of applications, including classic and collector cars
  • Iridium Power
  • Superior Performance: Engineered for maximum performance under extreme conditions, this spark plug delivers more horsepower, faster and easier starts, and fewer misfires under heavy loads.
  • Enhanced Fuel Efficiency: Thanks to its advanced design and patented technology, the Iridium Power plug improves fuel efficiency, making it an economical choice for your vehicle.
  • Low Voltage Requirement: The DENSO Iridium Power spark plug requires 5,000 volts less to fire compared to conventional spark plugs, ensuring reliable ignition with lower energy consumption.
  • Durable Iridium Material: Constructed with a durable iridium center electrode tip and a flat seat type, this spark plug offers long-lasting performance and reliability.
Specifications
Electrode Core Material:
Copper

Electrode Tip Material:
0.4mm Iridium

Ground Strap Quantity:
1

Insulator Type:
Purified Alumina

Manufacturer Heat Range:
16

Material:
0.4mm Iridium

Reach:
3/4 in

Resistor:
Yes

Seat Type:
Gasket

Thread Diameter:
14 mm

Tip Configuration:
0.4mm Iridium

Type:
Iridium Power

Wrench Diameter:
5/8 in
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4.67 out of 5
369 Customer Reviews
91% of respondents would recommend this to a friend
Ratings Distribution
5 Stars
309
4 Stars
34
3 Stars
5
2 Stars
7
1 Star
14
Denso does not replace AC Delco 41-125 OEM plugsBuyer bewareWould definitely purchase again.
Pros
41
Improves Engine Efficiency
34
Increases Power
32
Easy To Install
19
Durable
7
Lightweight
Cons
3
none
2
Decreases Gas Mileage
2
No Improvement In Performance
1
Difficult To Install
1
Not sure if will last as
Best Uses
40
Everyday Driving
26
Replacement
22
Performance Driving
7
Racing
5
Restoration
Car & Truck
10
Casual Driver
9
Auto Enthusiast
4
Mechanic
3
Competitive Driver
3
Truck Enthusiast
Describe Yourself
14
Auto Enthusiast
13
Casual Driver
9
Mechanic
4
Competitive Driver
1
Truck Enthusiast
Most Liked Positive Review
Go Denso
These plugs made my cobra mustang run alot better so I tried them in my everyday driver 05 Focus and now it runs alot better also. Just be sure and gap them at factory specs.I am suprised that they perform that much better than the NGK Iridiums that came stock! You will not be disappointed.
Most Liked Negative Review
Great in the beginning
I bought these plugs for a Pontiac G6 GT to liven it up. In the beginning they were great with a large difference in acceleration. However within 700 miles on the plugs this performance increase started to dive downward. My gas mileage went from 25 mpg to somewhere around 16 mpg with only about 2000 miles on the plugs. I currently am looking on the site for the stock delco part number to get my gas mileage and performance back. Right now with 2500 miles on the plugs my car has a rough idle, which will be gone once the Denso's are out! (Use them for race day and then take them out and reinstall your factory ones) For the price they are per plug they should last more than 2500 miles.
Reviewed by 369 Customers
Go Denso
Staff Reviewer -
These plugs made my cobra mustang run alot better so I tried them in my everyday driver 05 Focus and now it runs alot better also. Just be sure and gap them at factory specs.I am suprised that they perform that much better than the NGK Iridiums that came stock! You will not be disappointed.
Bottom Line Yes, I would recommend to a friend
Made a difference in my cars performance
Verified Buyer -
Finally changed the plugs in my Honda Civic, over 75,000 miles. I used the Iridium Power plugs and what a difference I could feel in the car's performance. I checked the gap as I took them from the box but they were were gapped perfectly out of the box. Very easy do it yourself project.
great tune up!!
Staff Reviewer -
i had doubts, but after installing these denso plugs i have zero regret. love it
Bottom Line Yes, I would recommend to a friend
excellent plugs for my Tiburon gs
Staff Reviewer -
I only have 25 miles use on them and noticed immediate improvements in idle and highway driving on a 2.0 liter 4 cyl. 5th gear on my car has much better acceleration. I can attest proof positive that the Denso IK16 Iridium has improved my engines performance enough to be noticed and not subtle. I have never noticed this much improvement changing spark plugs on a car till now !
Bottom Line Yes, I would recommend to a friend
Great in the beginning
I bought these plugs for a Pontiac G6 GT to liven it up. In the beginning they were great with a large difference in acceleration. However within 700 miles on the plugs this performance increase started to dive downward. My gas mileage went from 25 mpg to somewhere around 16 mpg with only about 2000 miles on the plugs. I currently am looking on the site for the stock delco part number to get my gas mileage and performance back. Right now with 2500 miles on the plugs my car has a rough idle, which will be gone once the Denso's are out! (Use them for race day and then take them out and reinstall your factory ones) For the price they are per plug they should last more than 2500 miles.
Bottom Line No, I would not recommend to a friend
Displaying Reviews 1 - 5Back to Top
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