laterongc

Sp546X vs sp546 spark plugs ( 5.4 3v plug motorcraft )

What are the “alleged” differences between sp546X vs. plain sp546, why the new model?

Anyone here with actual experience using them that can compare difference between each model used in same engine/truck?

is there a lifespan difference between the two?

laterongc

Ps: first heard of these from @Port11Gen post in a thread about autolite plugs. Hope he’ll drop in here and provide more details.

laterongc

Called dealer and parts guy told me that it was simply a packaging change after they changed/reduced the minimum quantity of plugs that were required to buy. Said it also came at same time as per unit price increase. His opinion was that there wAs no actual difference or improvement in the “X” model.

Port11Gen

hey laterongc, thank you for that specific dealer response to your inquiry. SP546/X are definitely the same plug, so no worries if someone cannot find the "X" series plugs. Just PLEASE don't substitute OEM Motorcraft for some lesser brand. I just changed out a set of champions someone had in and complained about poor performance after 1 year.

xxf150WL

twenty years ago you could call them champions. spark plugs were spark plugs, today not so much. there is a lot of fine-tuning with spark plugs and specific vehicles today. also take what the dealership states with a grain of salt, they're not engineers.

laterongc

Thanks for replying. Are you saying the X model is actually a different plug? If so, can you answer any of question in post 1? Thanks.

Port11Gen

Just purchased for 2005 5.4 3v.
This is the exact packaging straight from Ford. They reference the 2 as 1 if that makes sense.

Looks to be the same plug.
I will be contacting my Ford Tech on Monday to try and get a commited and solid answer on differences if any.

xxf150WL

Per the packaging, the SP546X and SP546 are "interchangeable."

As for specific engineering changes I have no clue. All I am stating is there had to be some type of design change to go above and beyond for Ford to create new packaging and a new catalog number. The guy in the parts department or service tech isn't going to know anything more than what they see on the computer screen. If Ford says they're "interchangeable" they are and they are liable. Always stay with major OE equipment when it comes to the drivetrain.

laterongc

@Port11Gen

what answer did they give you?

I happened to notice that they made similar change on sp509 and now a sp509x. Interesting thing is on oreilly they still lost both and the sp509x is $2/plug more than plain sp509 (8.99 vs 10.99)