5/8's should be OK, (16mm)
Try this link to help you know more...
https://www.fordfiesta.org/threads/spark-plugs.8693/post-23534 - and read thru several posts to help you
Did you catch what the thread talked about?
One main aspect is length of the plug, when it's installed - it's height of and depth of the plug sitting that far down - you'll not only need a reach but the well-depth of the socket and the SOCKET's own diameter can affect how far down the socket will drop of get (or fit) onto the Hex Nut the plug is resting in. Most of these T-handle ones don't provide the means of grip to help give you the torque you may need to back out the OEM (or the ones your replacing) due to the length of time they've been in the engines cylinder head and are now baked in - seized to the head. I'm saying - you'll need an extension (8" to 12" works here) in order to even get a ratchet wrench to even "crack" the nut loose and start backing it out.
Else this data for the
Recommended plugs this might help.
The Motorcraft SP-525X (part number CYFS12YECX) is an Iridium spark plug designed for 2011-2019 Ford Fiesta vehicles with a 1.6L non-turbo engine
. It is engineered to meet specific Ford performance and emission requirements, featuring a nickel-plated shell for corrosion resistance.
Key Specifications & Details:
- Part Number: SP-525-X / SP525X
- Interchange Numbers: CYFS12YECX, CYFS12YEC
- Material: Iridium
- Application: 2011-2019 Ford Fiesta (1.6L non-turbo)
- Features: Proprietary platinum pad on side wire electrode, nickel-plated shell
- Type: Spark plug
These spark plugs are designed to ensure proper combustion and engine efficiency for the specified Ford models
The above is for 16mm or 5/8" equivalent.
Once you get these plugs, check them with your tool, make sure they seat and slide into the rubber/silicone grommet that protects the porcelain from damage and chipping. And if you can't seem to find a method to get the old ones out, remember the ones you have in there may have a different Hex nut size - this may happen when you purchase a vehicle used. So the OEM ones might not be in there, they may have used another type as a cross reference to another brand that Ford doesn't recognize or use.
- That means the Hex Nut sizing may be different to get those out, than to put these in - the plugs used may need two different sockets to do this job.
Pay close attention to the
Interchange Numbers they are for Champion - and supply Ford with these plus they are re-badged for Ford's own inventory and are similar in fitment.
