Upgrade from OEM Motorcraft plugs (AGSF 22FSCM)
Originally Posted by Costas
"A litle off topic, but I can't decide between the NGK Iridium IX and Denso IT16, anyone running these with any comments?"
NGK Iridium IX I love them... and everyone else who uses them...
(I apologize for the tardy reply.) The answer is that ... it depends.
The OEM plugs are Motorcraft AGSF 22FSCM, which is a part number that the Motorcraft catalogue no longer recognizes. (Use a search engine to search for "AJTT-18-110" instead.) The OEM plug is a "double platinum" plug, which means that a tiny platinum disk is welded to the center electrode and another platinum disk is welded to the ground electrode. Platinum has a higher melting point than the nickel traditionally used for the electrodes, so the double platinum plugs wear much longer than old-style plugs. The OEM plug is also a "fine wire" design; that is, the center electrode is smaller in diameter than the center electrode of traditional plugs. The finer (smaller diameter) the center electrode is, the more efficient is the sparking (superior ignitability).
The two giant and leading Japanese makers of spark plugs each offer an "ultimate" upgrade from the OEM plug, each with an advantage over the other: NGK ITR5F13 (also known as NGK 6044) in NGK's "Laser Iridium" series, and Denso IT16 (also known as Denso 5325) in Denso's "Iridium Power" series. More recently than Denso and NGK, Bosch has introduced a line, "Iridium OE." that competes head-to head with the other two; the applicable part is Bosch 9657.
The NGK ITR5F13 /6044 is an iridium/platinum plug: it has the same kind of platinum disk welded to the ground
electrode as the OEM Motorcraft plug, but the center electrode is made of an iridium alloy that is harder and stronger, and has a higher melting point, than platinum. Because of its strength, the NGK's iridium center electrode can be made as small as 0.6 mm in diameter, which is even finer than a fine wire platinum plug's center electrode. The NGK ITR5F13/6044 has outstanding wear characteristics, with half again the predicted service life of the OEM Motorcraft plugs under the same operating conditions, and -- possibly -- some modest performance advantages (marginally better power, marginally better fuel economy) over the OEM plugs, as well.
The Bosch 9657 has a construction that is very similar to the NGK ITR5F13, and Bosch claims that the "continuous 360°" laser welding process it uses -- the same welding process that Denso uses -- is superior to the laser welding process that NGK uses.
The Denso IT16/5325 is an iridium spark plug that features an even finer central electrode -- 0.4 mm vs.
the NGK's 0.6 mm -- and also a unique (it is patented) U-shaped grove in the ground
electrode that fosters the generation of a fatter, rounder spark and more efficient ignition. As a result, the Denso design possibly
will give slightly greater power and slightly greater fuel economy than the NGK ITR5F13/6044 plug. See: http://www.svtlightnings.com/sparkplugmisfires.htm
Win-win, right? But there is a catch.
All electrodes wear themselves out just from normal operation; every spark it generates, the electrode sacrifices a tiny part of itself. But the center electrode of the Denso IT16/5325 is so fine to begin with, it has less of itself to give. Also -- and this is mildly shocking (pun intended) -- the ground electrode of the Denso Iridium Power series plugs that feature the U-shaped groove is an ordinary nickel alloy, not enhanced with a welded-on platinum disk as in the NGK ITR5F13/6044 or iridium-platinum insert as in the Bosch 9657. Platinum has a higher melting point than nickel and wears better than nickel, so, between faster wear of the fine center electrode and the faster wear of the nickel alloy ground electrode, the service life of the Denso IT16/5325 is only about one quarter of the service life of an NGK ITR5F13/6044 or Bosch 9657. Thus, if you change plugs at about the 75,000 mile mark as recommended in the service manual for the Mazda6 V6, a changeover to the NGK ITR5F13/6044 will leave you good to go to about 200,000 miles on the odometer, while a changeover to the Denso IT16/Denso 5325 plugs will leave you needing another change of plugs soon after 100,000 miles. If you are paying a mechanic to change the plugs on your Mazda6, the modest fuel economy advantage of the Denso over the NGK probably will not cover the additional labor charges for the repeated plug replacements.
Incidentally, as fullyarmed101
points out, NGK makes a nominally higher performance "IX" series of plugs that, like the "Laser Iridium" series plugs, feature an iridium center electrode; the applicable IX plug for the Mazd6 V6 is TR5IX (NGK 7397). The center electrodes of the NGK IX plugs are the same 0.6 mm as the center electrodes of the NGK Laser Iridium iridium-platinum plugs (that is, not as fine as the Denso's 0.4 mm), and the ground electrodes of the NGK IX series plugs, like the Denso Iridium Power series's ground electrodes, are plain nickel alloy; and the NGK plugs lack the U-shaped groove that characterizes the ground electrodes of the Denso Iridium Power plugs, so the Denso Iridium Power plugs possibly retain a slight performance advantage over the NGK IX series plugs. As the price per plug of the two serieses of NGK plugs is about the same, there is no reason to choose an inferior NGK IX single iridium plug (7397) over a superior NGK Laser Iridium iridium/platinum plug (6044).