dabangsta Posted April 22 Report Share Posted April 22 I bought the SP550X as specified in the owners manual, which in the old part number scheme is CYFS12YPCTX (which each set of letters and numbers can be decoded), but they also show SP594 when I put in my VIN at fordparts.com SP550(X) - CYFS 12 YPC TX SP594 - CYFS 12 YR T3 The first group of letters are the thread, reach, seal type. 12 is the heat range. the suffixes includes ones I have never seen before, and all decoders I can find don't include these (like EE or PP is Double Platinum, N is Nickel) Anecdotally the shell/threads look like a different material, like nickel versus something else shiny but more golden hue (stick with me here...). I am going to put in the SP550 but curious if anyone knew how to decode the suffix and what the difference in these plugs are. I already know that SP550X supersedes the previous SP537 (CYFS 12 Y2) Quote Link to comment Share on other sites More sharing options...
dabangsta Posted May 23 Author Report Share Posted May 23 I think changing them out at 82,000 miles has improved the idle a bit, was a wee bit rough before. I fought the cylinder #4 COP until I figured out how easy these boots come off the COP and how. I was surprised to see this much carbon on the insulator porcelain (I wiped away some on the first one to check the part number): The Iridium nub was still shiny but the gap was eroded a bit Quote Link to comment Share on other sites More sharing options...
1004ron Posted May 23 Report Share Posted May 23 17 minutes ago, dabangsta said: I was surprised to see this much carbon on the insulator porcelain (I wiped away some on the first one to check the part number): That's corona stain which isn't an issue. 5 Things You Should Know About Spark Plugs - NGK Spark Plugs What is Corona Stain? - NGK Spark Plugs Australia | Iridium Spark Plugs | Glow Plugs | Oxygen Sensors | Ignition Leads | Ignition Coils : NGK Spark Plugs Australia | Iridium Spark Plugs | Glow Plugs | Oxygen Sensors | Ignition Leads | Ignition Coils 1 Quote Link to comment Share on other sites More sharing options...
dabangsta Posted May 23 Author Report Share Posted May 23 39 minutes ago, 1004ron said: That's corona stain which isn't an issue. 5 Things You Should Know About Spark Plugs - NGK Spark Plugs What is Corona Stain? - NGK Spark Plugs Australia | Iridium Spark Plugs | Glow Plugs | Oxygen Sensors | Ignition Leads | Ignition Coils : NGK Spark Plugs Australia | Iridium Spark Plugs | Glow Plugs | Oxygen Sensors | Ignition Leads | Ignition Coils Interesting, I didn't know that is what it was called, and what it really was. I have seen a tan and brown film before, but never this much depth and darkness. I guess my other cars with the plugs down in wells the spark plug boot covers more up to the shell, and before that when plugs where out in the elements it was tough to tell road grime from it. I did the plugs on an older 2.0 with 110,000 miles and it had none of that, I always thought it was combustion gases making it past where the shell was, as I have seen it on one or 2 plugs but never all of them. 2 Quote Link to comment Share on other sites More sharing options...
STBEAST Posted May 23 Report Share Posted May 23 Learn something new every day. Great information. Thanks for that. 1 Quote Link to comment Share on other sites More sharing options...
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