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Best Spark Plugs for Ford Ecoboost 3.5l Engine:

This goes without saying the most important thing to do is to change your spark plugs on any Ecoboost Ford much more often than you might think. Some people recommend as low of an interval as every 15,000 miles. That would be for very aggressive driving habits and if you are constantly racing your truck or pushing it hard on off-road etc. What you might start to notice in your ecoboost 3.5l if the plugs need to be changed is the car shaking at idle or missing. It might throw a check engine code either for a specific misfire code on a certain cylinder or if you can read Mode 6 data check for misfires on different cylinders. Read my article about Mode 6 data here.

To get straight to the point the best Spark Plugs for an Ecoboost 3.5l as found in many Ford F-150 trucks etc., are the Motorcraft SP-534 plugs. When receiving the plugs whether you buy them at the dealership or the Amazon link above– make sure you at least check the gap on the plugs and re-gap them to 0.028″. What is more important than gapping them exactly is making sure there are none that you receive that are far off on gap. That can have huge performance losses if one or two of them is gapped incorrectly. Please be advised that this is a common error with these spark plugs in general coming with wrong gaps when buying new. In order to be able to correctly check the gap of these plugs make sure you buy some high quality feeler gauges and know how to use them properly. Do not attempt to gap spark plugs without watching many videos and feeling confident in your ability.

Why do Ford Ecoboost Engines Need New Spark Plugs So Often?

The Ecoboost 3.5l found in many Ford trucks eats spark plugs. Why? It is hard to say, it could be a bit of quality control problems from Motorcraft and Ford in general. It might also be important to realize these engines are turbo charged which can lead to faster spark plug degradation. It might also be important to note that people might enjoy driving this engine and truck harder than normal, and therefore might be putting more stress on the spark plugs. Luckily they are not very difficult to change, with some basic knowledge and tools you can do it yourself.

How to change spark plugs in Ford Ecoboost 3.5l?

The first thing you’re going to want to do is remove the oil cap so we can get the engine cover off
Lift the cover upwards and then pull the cover forward towards you.
Set the cover aside and put the oil cap back on.
If your engine bay is dirty spray compressed air around each of the coils and remember being clean is always better. You don’t want dirt and debris falling down the open holes when you remove the spark plugs.
Start on the passenger side first and unplug the ignition coils by taking the red tab and slide it back.
You may need to use a little pocket screwdriver or pick to help you get the connectors off. Do not fight them and try not to break them.
Push the little tab downwards and then pull the ignition coil plug off.
1. Pro Tip: It helps to push the connector all the way in towards the coil and then push the tab down and then pull it off.
Remove the 8mm (eight millimeter bolt) holding down the ignition coil to the valve cover.
Pull the coil out and twist as you pull up to break the seal from the boot on the spark plug.
Do the same thing for the two remaining coils on passenger side.
On the driver side you’re going to need to remove the foam pad that is blocking your access and a couple of other things to get better access.
It is best to wait until the engine has reached room temperature before doing this as for the rear passenger one you might be up close to the heater hoses and burn yourself if not.
Use a 5/8 standard spark plug socket and some extensions to reach all the plugs. I really like magnetic spark plug sockets as they do the best job in 2021.
the original spark plug does not have anything on the threads no anti-seize. I however recommend using some Nickel Anti Seize from Motorcraft (a tiny bit goes a long way)
The gap is supposed to be set on the plugs from the factory but double check them to make sure the gap is correct and close on all
Be careful with the tip of these plugs as they are very fragile and can break easily. If the plugs are far out of gap it is best to just go return them and exchange them for properly gapped ones.
Thread the new spark down until it bottoms out by hand. Torque the spark plug to 11 ft-lbs or if experienced just use the good-n-tight feeling.
Put the coil back on the cylinder and re-tighten the 8mm fastener holding the ignition coil to the valve cover. The torque spec on this bolt is not super important, just get it moderately tight (do not break it) and you’re good. It is a no stress type bolt that isn’t having to work very hard. The actual spec is 5 ft-lbs for these.
Driver side you need to unplug the tab on the bottom of the high-pressure pump. Press upwards and squeeze the tab and pull the connector off so that we can get to the coil.
Also remove the vent line by getting the little tab backwards about a 1/4″ and then pull upwards and release it. Twist it out of your way.
Repeat the same process removing anything that is in your way to reach the 8mm bolt holding down the coils. Reinstall the new properly gapped plugs and torque everything to spec.

What Tools Do I Need To Change Plugs Ecoboost?

You will need various extensions, ratchets, and metric and SAE sockets. The most important ones you will need are a 5/8″ spark plug socket and an 8mm socket to remove the ignition coil bolts. A variety of extensions and having metric sockets in both 3/8″ drive and 1/4″ drive make doing these jobs easier as you can choose which size socket to use based on how much space you have.

What size spark plug socket do I need?

For the Ford Ecoboost 3.5l engine you will need a 5/8″ spark plug socket. You can likely use a 16mm deep socket as well and then use a magnetic tool or the boot of the ignition coil to remove the plug from down in the spark plug hole. With anything please be careful of not breaking the porcelain on the plugs, not dropping them down into the spark plug hole, and not letting dirt, debris, or bolts fall down into the cylinder.

How often should I change the plugs on my 3.5l Ecoboost Ford?

I would recommend doing them every 50,000 miles based on my reading of forum users and because they are relatively easy to change. If you start to notice misfiring, check engine code, a flashing check engine light, a hiccuping in the truck, a loss of MPG or performance, it might be time to at least check the gap on the plugs and make sure none of them have cracked porcelain or other problems. Some people change their spark plugs every 10,000 miles on these trucks. If you ask me that is excessive and might lead to more problems than it is worth, but still worth noting some people think that is what these trucks need. For more info check out this forum search here. Ford says every 100,000 miles for normal interval or every 60,000 for special functions. Well if you drive your truck hard ever you probably should go with the special interval and change them at least every 60,000 miles. They are only around $5 each, so just do it.