Another Spark Plug Thread

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Aug 30, 2004
Many OEMs are reducing the spark plug replacement interval on their direct-injected engines. Mercedes is at 50k, Mazda is at 75k (40K for the new CX9), Toyota is at 60K. The below plugs were removed from a 2013 Mazda 3 skyactiv after 73,451 miles. The OEM spark plug replacement interval is 75,000 miles. The car does idle noticeably smoother after the spark plug replacement. I replaced these plugs with NGK 94124 (ILKAR7L11).
They don't look that bad. I remember the days of changing them every 10K miles. How far off was the gap from spec?
Originally Posted By: demarpaint
They don't look that bad. I remember the days of changing them every 10K miles. How far off was the gap from spec?
I did not measure the gap. There are some carbon deposits, but they are not too terrible. Overall, 75k does seem a bit on the early side, but I am just going by the manufacturer’s recommendations.
I believe Mercedes lowered it when they went with a multi spark ignition system where the plugs can fire up to 4 times per cycle in their direct injection engines.
Bought Denso iridiums from eBay and in less than 20k mi the gap went to 0.063-0.076 range on all plugs. Now I was looking for oem and was packaged and engraved flawlessly, but it turns out it was bogus. The OE stuff was 0.050 or so after 73k mi. So 60k interval is fair. Spot the fake, they are all different part numbers. Used to be able to buy brand name stuff on eBay, not anymore... rs.
Just retired the second set of plugs in my ‘11 Ecoboost F150. When they went bad, they went fast! Fine one week, shot the next, replete with missfires, almost like bad gas. The factory set made 60k, the second set made 50k and now on to this new set. The out going plugs had wider gaps than I remember setting them to. Very little carbon. This new set went in at .028. So far so good - took her out for an Italian tune and she’s good to go. All 3 sets were Motorcraft, with the second set being a different part# from the factory ones. #3 same part number as #2. Truck odo almost at 111k.
I replaced the plugs on my 03 V8(4.7L) 4Runner at 100K because that's the factory recommendation. They looked good and the gap was just slightly out of spec, maybe a few thousands. A Toyota dealership mechanic told me that the plugs on the 4.7L V8 almost always come out at 100K looking good. I was concerned about all the problems I've heard with removing spark plugs on these late model engines but these came out with no problems. I can remember when plugs wouldn't last 10K miles in the days of breaker point ignition system. When I installed my first after-market solid state ignition system I was happy to not have to set the dwell and timing anymore.
Thanks for the post Critic, The. My sister has a 2012 Mazda3 with the 1998cc Skyaktiv engine so I have to ask her what her mileage is. She has a consistent mileage record of 1,000 mi. per month. It's almost eerie.
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