Denso (5304) IK20 Iridium Spark Plug, Pack of 1

Picked up a set of these to replace the stock NKGs on my 2005 Honda Accord 4 cylinder after 97k miles. The originals were still good -- just doing a spring-time overhaul.

Engine felt smoother although that could be psychological. What is real, however, is a solid and consistent 2 MPG increase in fuel economy from what I was averaging over the last 60k miles.

I'll try to update this review after 30k miles or so.

This fits in 1999-2003 Toyota Sienna. Trick to replace the three spark plugs in the back is to remove the windsheld wipers and the plastic piece for intake air and rain water collector -- a big piece from left to right.

After the spark plugs replaced, the engine runs smooth, starts faster. Since Iridium is very expensive, the tip is little -- 0.4mm in size, so that it can spark easily. Denso's web site says it has life 60,000 miles. Denso also developed one for Toyota and Lexus that has 0.7mm tip, that one can last 120,000 miles. 0.4mm has more precise ignition time, so that better fuel econemy.

Until recently, platinum was considered the best material to use on the top of an electrode because of its durability. However, Iridium is 6 times harder, 8 times stronger, and has a melting point 1200 degrees higher than platinum. Put that into a harsh environment such as an engine piston chamber, and you have a spark plug that can resist wear much better than...Read more

I just installed a set of these in my 2001 GL1800. I previously had NGK standard plugs with under 1,000 miles on them and AC Rapidfire plugs with 24,000 miles on them.

The AC Rapidfire plugs were my previous favorite, but it seems they are not the same plug anymore, having lost the serrated center electrode. The Rapidfires I had previously installed were the non-serrated type. They still provided faster starts than new NGK plugs, but not the improvement I had witnessed in other engines with the serrated Rapidfires.

The IK20s, which, in spite of the title and picture, are Iridium Power plugs, provided about a 1/2 second start time, where new NGKs gave a slightly longer than one second start, and the Rapidfires gave a slightly less than one second start. The engine is running smoother than with the 24,000 mile Rapidfires, but that is no suprise. I can't tell if it is running smoother than with new Rapidfires, as the difference is negligable. That is the...Read more