Are there any downsides to using a one strep colder plug, without a tune?

 

Probably not, but no upside either.

 

Mine is tuned, Ford updated the plug spec 3 times since 2015, latest plug is warmer than the original spec. Truck runs fantastic. I do reduce the gap to .027".
Use the latest recomemended spec Motorcraft plugs for best performance and efficiency.

 

Ford engines are sensitive to brand and gap. It’s all risk no reward to go colder on modern engines. Unless required by a tune.

 

Thanks for the replies. For some unknown reason, I have two boxes of cold plugs for my tuned SHO, and was wondering if I could avoid buying another set of regular plugs for the F150.

 

Colder plugs in a stock tuned engine will wear out faster due to soot. My 2017 2.7 came with cold SP542 plugs from the factory. These were superseded with a hotter plug and then a modified tip I think the Ford cold performance plug for Ecoboosts is the SP542-28 part# M-12405-35T. The Ford Performance Plug is made by NGK.
I use NGK 6510s in my tuned 2.7, they look identical to the SP542s, gaped at .025 they get changed out every 20000 miles before any problems pop up. KM

 

I just went though this on a used '16 2.7 EB 116k service. Ford spec went from SP542 to SP578 and finally SP594. They appear to to cross to NGK. What's funny, the plugs that came out were NGK. Still working and showing the mileage. NGK LTR6IX Iridium. I didn't bother to try and cross reference them. I was pleased that they were Iridium. To my knowledge, Iridium originated as an aircraft duty plug. Less resistance and greater corrosion protection than Platinum. They used to be $10+ a piece and I put some in a 4.0 Ranger back then. These plugs are super durable and will easily go 100k miles with normal operation.

 

The 6510s I use are LTR7IX-11. the 7 indicates heat range and NGK grades heat with lower numbers so the LTR6IX is a range hotter plug. KM

 

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1. why?
2. better to read the plugs overall condition to see what the engine is doing / conditions is, and your driving application for accessing a change in heat range.
3. running Lean, Rich or using Oil.
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Plugs are a compromise for all these and determine life span besides the Heat flow to the Heads.
Any obvious faults with fuel delivery and combustion should be cleared first.
a. Fuel Tables shifted too Rich or Lean on One or both Banks
b. Misfires, what cylinders and why.
No one can really tell you without knowing these conditions.
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Good luck.