What size is a Ford Fiesta spark plug?
The correct spark plug size depends on the Fiesta’s engine and year, so there isn’t a single universal size. In practice, most modern Fiests use a 14 mm threaded plug, while some smaller EcoBoost variants may use a 12 mm thread. Always verify the exact size by engine code or VIN before buying.
Engine variants and spark plug sizing
Because Ford has used multiple engines in the Fiesta across generations, plug thread size and reach vary. The most common size across many non-turbo Fiesta engines is a 14 mm thread. Some 1.0-liter EcoBoost variants use a smaller 12 mm thread. The reach, heat range, and recommended gap also vary by engine. Always verify with the exact engine code.
Common sizes you may encounter on Fiesta engines include the following:
- 14 mm spark plug thread (M14x1.25) is standard on many Duratec-based engines used in the Fiesta's mid- and larger-displacement variants.
- 12 mm spark plug thread is used on some smaller EcoBoost variants, notably certain 1.0-liter engines.
- Other sizes exist for very specific markets or earlier generations; consult the manual for your exact model.
Note: the above reflects typical cases; always confirm your model’s exact spec before purchasing plugs.
How to identify your exact spark plug size
Use these steps to determine the exact plug size for your Fiesta.
- Check the owner's manual or Ford workshop manual for the spark plug specification by engine code.
- Find the engine code in the VIN plate or under the hood; this code identifies the correct plug type.
- Look up the exact part number in Ford's official parts catalog or a reputable parts retailer using your engine code or VIN.
- Inspect the spark plug in your engine to verify thread diameter and reach; match the old plug to the new one.
- When in doubt, contact a Ford dealer or a qualified mechanic with your VIN to confirm the correct plug size.
By confirming the engine code and, if necessary, comparing the threads, you can be confident you have the correct spark plug size for your Fiesta. Using the wrong size can damage threads or cause improper sealing and misfires.
Gap and torque basics
The required spark plug gap and tightening torque depend on your engine. Typical gaps for many modern plugs run around 0.028–0.032 inches (0.7–0.8 mm), but you must verify the exact specification for your engine. For torque, follow the Ford service manual; over-tightening can strip threads and under-tightening can lead to poor sealing or misfires.
Summary
The Ford Fiesta does not have a single spark plug size. The correct size varies by engine code and model year, with 14 mm threads being the most common and 12 mm used on some EcoBoost variants. Always consult the vehicle’s manual or a Ford dealer/parts catalog for your exact engine, and verify by engine code or VIN before purchasing plugs.
What size spark plugs are in a Ford Fiesta?
NGK 97576 Spark plug for FORD FIESTA M12 x 1,25, Spanner Size: 14 mm.
What size socket is a Ford spark plug?
For the majority of plugs, you need a 5/8” or 16mm socket. Some Fords use 9/16″ plugs, some newer European and Asian vehicles use 14mm plugs, and there are a few applications that use 7/8″, 13/16″, ¾” or 18mm plugs.
What size socket for Ford Fiesta spark plugs?
The Ford Fiesta spark plug socket size is 5/8 inch (or approximately 16mm) for many models, but for EcoBoost engines, you will need a 14mm double hexagon (bi-hex) deep socket. It's crucial to confirm the exact size for your specific engine model, as a general 14mm socket will not work for EcoBoost engines, which require a special thin-wall 14mm Bi-Hex socket.
This video demonstrates how to replace spark plugs on a Ford Fiesta (2011-2019): 53sTRQYouTube · May 2, 2022
Socket sizes by engine type
- Most standard engines: A 5/8 inch (approx. 16mm) deep spark plug socket is needed. This is the most common size for older or non-EcoBoost engines.
- EcoBoost engines (1.5L): A 14mm double hexagon (bi-hex) deep spark plug socket is required. This is a special, thin-wall socket designed for tight clearances and the specific plug type used in EcoBoost engines.
Important considerations
- Always check your vehicle's specific requirements: The correct socket size can vary depending on the engine. It is best to check your owner's manual or a reputable online forum for your exact year and model to be sure.
- Use a dedicated spark plug socket: These sockets have a rubber insert to grip the spark plug and a long, thin wall to access it in the deep spark plug wells.
- Consider a thin-wall socket for EcoBoost engines: A standard 14mm socket will not fit; you need the thin-wall, double-hexagon type to clear the spark plug well.
How do I know what size my spark plug is?
If you're in doubt, you can pull a spark plug out and check the number printed on it, using it for a cross-reference. Another way to check is to enter your vehicle's information online, or by checking with an in-store associate at your local AutoZone.
