What size socket for Ford Fiesta spark plugs?
For the vast majority of Ford Fiesta petrol engines, the spark plug hex size is 14mm, so you’ll typically need a 14mm spark plug socket (usually on a 3/8-inch drive) with a rubber insert to hold the plug securely while you work. A small number of older or market-specific variants use a 16mm hex, so it’s smart to double-check your exact engine code and year before buying tools.
Fiesta generations span multiple decades and engine families, including the Duratec line (1.25, 1.4, 1.6) and the later EcoBoost 1.0. This article explains the usual socket size, how to verify the correct size for your car, and tips for a safe spark plug replacement.
Common plug sizes by engine family
Most Ford Fiesta petrol engines still use the standard 14mm hex spark plugs, so a 14mm spark plug socket is the right choice in the vast majority of cases. This section breaks down the main engine families and what to expect when you shop for tools.
1.0 EcoBoost (three-cylinder)
In typical Ford Fiesta EcoBoost applications, the spark plug hex is 14mm. Use a 14mm spark plug socket (on a 3/8-inch drive) with a long extension for access. Always verify with your exact engine code, since last-generation or regional variations can differ.
Duratec family (1.25, 1.4, 1.6)
These engines generally use 14mm spark plugs as well, with the standard 14mm plug socket. As space is often tight, a long-reach socket and/or flexibility joint may help in accessing the rear cylinders, but the hex size remains 14mm in typical configurations.
How to confirm the correct socket size for your Fiesta
Before attempting a plug change, check the correct size against official documentation or the plug you’re replacing. Use the steps below to confirm the right tool.
- Consult the owner's manual or a workshop/repair guide for your specific Fiesta model and engine code to confirm the spark plug specification.
- Remove a plug or inspect the existing plug head and measure the across-flats (the hex size) with a caliper or a ruler; common sizes are 14mm or 16mm.
- Check the spark plug packaging or part number; the packaging often indicates the socket size required.
- If in doubt, take the plug to an automotive parts counter and have staff confirm the socket size for your engine.
Using the right size avoids damaging the plug or gear and ensures you can thread the new plug properly. If you’re unsure, consult a professional mechanic to confirm the exact requirement for your vehicle's VIN/year/model.
Summary
Across most Ford Fiesta petrol engines, a 14mm spark plug socket is the expected standard, paired with a 3/8-inch drive. While 14mm is typical, some variants may use a 16mm hex. Always verify using your engine code or official manuals to ensure you’re using the correct socket for a safe, effective spark plug replacement.
What size socket for Ford spark plugs?
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. All spark plugs are 6 sided, except some BMW engines.
What size spark plug socket for Ford Fiesta 1.0 EcoBoost?
3/8"
3/8" spark plug socket for EcoBoost engines, 14 mm.
What size spark plugs are in a Ford Fiesta?
NGK 97576 Spark plug for FORD FIESTA M12 x 1,25, Spanner Size: 14 mm.
How to change spark plugs on a 2015 Ford Fiesta?
Member
- Start off by lifting up the engine cover.
- Unplug the spark wires by pulling back the small white tab until you hear two clicks.
- Unbolt 8mm bolts holding the coilpack.
- Remove the coilpack by pulling it up.
- Loosen the spark plug by using the spark plug socket.
- Remove the sparks and see its condition.
