Spark plug gap

[TylerBoy54]

I have a 2015 mustang eco-boost with no tune. I had my spark plugs changed over the weekend, Picked them up at AutoZone with a .028 pre-gap, Ford Motorcraft plugs. My mechanic insisted that the correct gap for my car was .031. So he adjusted the gap. Is .031 the correct gap for my vehicle? The car is running smoother than it was, but I’m just curious on what the correct gap size is?

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[Skye]

https://www.fordservicecontent.com/...-Owners-Manual-version-3_om_EN-US_03_2015.pdf

Looks like you're both right. If you feel the engine operates better at .031, no further action required.

 

[Torched10]

https://www.fordservicecontent.com/...-Owners-Manual-version-3_om_EN-US_03_2015.pdf

Looks like you're both right. If you feel the engine operates better at .031, no further action required .048 to 053

Your link shows. 048
I've been gapping spark plugs for 40 years on big blocks and they're generally from .028to .035

 

[Skye]

Your link shows. 048
I've been gapping spark plugs for 40 years on big blocks and they're generally from .028to .035

The OP explained he had a 2015, EcoBoost. The link I provided is the 2015 Owners Manual; the chart above is from that manual. If one scrolls to printed page 268, the specification for the "2.3L I4 Ecoboost" is '.027-.031in".

Regarding the V6 and V8 units, Ford's gap for 2015 was ".049-.053 in" when using the "SP-520 / CYFS-12F-5" [V6] and "SP-519 / CYFS-12Y" [V8] spark plug, respectively.

As an exercise, I rolled through Ford Owners Manuals, from 2016-2023. I was curious, if, with emissions or other equipment changes, the gaps were adjusted over time. Aside from one later change (of .001 of an inch), they are surprisingly consistent for years 2015-2023, Ecoboost. For 5.0L V8s, there've been no changes in the gap, from 2015-2023.

I can't speak as to if adjusting the gap tighter or looser than Ford lists for a given year and engine type would benefit me or anyone else. For a stock engine, I'm going to continue to follow the manufacturer's specification.

If an engine has been modified, I'll ask or confirm with those vendors if any specs should be adjusted to support those equipment changes.

YMMV.

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