FYI SP-542 successor is NOT the SP-578

[nikhsub1]

Went down this rabbit hole while on lockdown. The SP-578 is now the OEM plug for our trucks that is one step HOTTER than the old SP-542. The revised colder plug is now part number M-12405-35T, I don't believe there is an SP# associated with them anymore. The plugs are redesigned, have thinner material around the electrode (when comparing the 542 to the M-12405-35T) but the M-12405-35T is the replacement and is one step colder than OEM. The part number printed on the plug itself is cyfs 092 ypt 3. The important notation in that is the 092 - if you read this Motorcraft guide to spark plugs (see page 8) in the second block from the bottom you will see 'first number' - in this case it is 09. The SP-542's printed part number on the plug itself is: cyfs 092 ypt (note it is missing the 3, otherwise identical).

http://www.fordinstallersupport.com/files/catalogs/spark.pdf

The SP-578 has this part on it: cyfs-12y-pt. This is our STOCK PLUG. If you again, refer back to the legend at the link above, you will see that the first number here is 1, which is listed as a cold plug. The SP-542 successor's first number is 09, listed as extremely cold and one step colder than the SP-578. Also, when I went to parts.ford.com and put my VIN in and searched spark plugs, this came up:

Spark PlugPart #: SP578 (12Y) <---- Note the 12Y
Service Plug May Differ From Original, 09/26/2016, F-150, 3.5L V6 GTDI

In conclusion, and for the tl;dr crowd, the SP578 is the OEM plug, it is NOT the SP542 equivalent. The SP542 successor is indeed the M-12405-35T

 

[Biggwrm]

Went down this rabbit hole while on lockdown. The SP-578 is now the OEM plug for our trucks that is one step HOTTER than the old SP-542. The revised colder plug is now part number M-12405-35T, I don't believe there is an SP# associated with them anymore. The plugs are redesigned, have thinner material around the electrode (when comparing the 542 to the M-12405-35T) but the M-12405-35T is the replacement and is one step colder than OEM. The part number printed on the plug itself is cyfs 092 ypt 3. The important notation in that is the 092 - if you read this Motorcraft guide to spark plugs (see page 8) in the second block from the bottom you will see 'first number' - in this case it is 09. The SP-542's printed part number on the plug itself is: cyfs 092 ypt (note it is missing the 3, otherwise identical).

http://www.fordinstallersupport.com/files/catalogs/spark.pdf

The SP-578 has this part on it: cyfs-12y-pt. This is our STOCK PLUG. If you again, refer back to the legend at the link above, you will see that the first number here is 1, which is listed as a cold plug. The SP-542 successor's first number is 09, listed as extremely cold and one step colder than the SP-578. Also, when I went to parts.ford.com and put my VIN in and searched spark plugs, this came up:

Spark PlugPart #: SP578 (12Y) <---- Note the 12Y
Service Plug May Differ From Original, 09/26/2016, F-150, 3.5L V6 GTDI

In conclusion, and for the tl;dr crowd, the SP578 is the OEM plug, it is NOT the SP542 equivalent. The SP542 successor is indeed the M-12405-35T

Can also confirm from hands on experience. M-12405-35T only way to get them now.

 

[engine45]

Went down this rabbit hole while on lockdown. The SP-578 is now the OEM plug for our trucks that is one step HOTTER than the old SP-542. The revised colder plug is now part number M-12405-35T, I don't believe there is an SP# associated with them anymore. The plugs are redesigned, have thinner material around the electrode (when comparing the 542 to the M-12405-35T) but the M-12405-35T is the replacement and is one step colder than OEM. The part number printed on the plug itself is cyfs 092 ypt 3. The important notation in that is the 092 - if you read this Motorcraft guide to spark plugs (see page 8) in the second block from the bottom you will see 'first number' - in this case it is 09. The SP-542's printed part number on the plug itself is: cyfs 092 ypt (note it is missing the 3, otherwise identical).

http://www.fordinstallersupport.com/files/catalogs/spark.pdf

The SP-578 has this part on it: cyfs-12y-pt. This is our STOCK PLUG. If you again, refer back to the legend at the link above, you will see that the first number here is 1, which is listed as a cold plug. The SP-542 successor's first number is 09, listed as extremely cold and one step colder than the SP-578. Also, when I went to parts.ford.com and put my VIN in and searched spark plugs, this came up:

Spark PlugPart #: SP578 (12Y) <---- Note the 12Y
Service Plug May Differ From Original, 09/26/2016, F-150, 3.5L V6 GTDI

In conclusion, and for the tl;dr crowd, the SP578 is the OEM plug, it is NOT the SP542 equivalent. The SP542 successor is indeed the M-12405-35T

thank you for this info Nikhsub1 I’ve been sitting on a set of sp578 plugs and was leary of putting them in. Just ordered a set of m-12405-35t . You get 6 thumbs up sir

 

[ljn21]

Who has the best price on the m-12405-35t?

 

[engine45]

I ordered from cjpony parts. And got a lil discount. So pay attention you’ll see it

 

[ljn21]

Can also confirm from hands on experience. M-12405-35T only way to get them now.

What do they come gapped at? I see conflicting info online that they come 0.031 and 0.028. What were yours gapped at?

 

[P4mnceBlue82]

I'm going to put these in as well when I change. Are you changing based off of milage or just bc you want to change? I'm trying to figure out at what point to change the plugs.

 

[nikhsub1]

I usually swap them out every other or every 3 oil changes - i use 5k mile OCI.


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[TXRaptor]

I usually swap them out every other or every 3 oil changes - i use 5k mile OCI.


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Have you noticed any problems with the plugs you have changed at 15K miles? My 2018 has 14K miles so I may change my SP-542s when I do my third oil change after the restrictions are lifted.

 

[nikhsub1]

Have you noticed any problems with the plugs you have changed at 15K miles? My 2018 has 14K miles so I may change my SP-542s when I do my third oil change after the restrictions are lifted.

I noticed the truck not idling quite as smooth - of course, it felt like butter after the change but it's probably psychosomatic.