Spark plugs are one of the most critical components inside your engine that need to be maintained. There’s a decent probability you will need to replace your worn out spark plugs several times over the course of owning a 2008 Subaru Impreza. Spark plugs are one of the most critical components inside your engine as they begin the entire combustion process that starts and keeps your engine running for many thousands of miles. Like most engine parts, spark plugs experience wear over time and eventually need replacement, but fortunately this is a repair you can do on your own. Odds are, if you’ve found yourself here, you have no idea how to do that, or potentially you’d just like to know what kind of spark plugs you need to buy. The entire process of changing your spark plugs should take about 20-45 minutes. This article will go over everything you will need to know about your Subaru Impreza’s spark plugs, whether you need some general information or a full, step-by-step guide to performing a spark plug change.
Correct spark plugs on a 2008 Subaru Impreza
Recommended 2.5L H4 2008 Subaru Impreza Spark Plugs
Recommended 2.5L H4 Turbocharged 2008 Subaru Impreza Spark Plugs
These spark plugs are an exact fit for their respective engines and will match the required specifications. As this 2008 Subaru Impreza features a 4 cylinder engine, ensure you purchase 4 spark plugs. We always try to recommend the best possible spark plugs for the money, and these spark plugs are either a factory recomendation or an equivalent replacement available in today’s market at an affordable price.
How often should I change my spark plugs?
As a general recommendation, it is advised that you replace spark plugs once every 20,000 to 40,000 miles. Of course, please make sure to check your owner’s manual to determine the exact interval determined by Subaru for the 2008 Impreza. Of course, if you drive your vehicle more aggressively or own a Impreza with some modifications, you may want to consider changing your spark plugs closer to the 20,000 miles end of that spectrum.
However, there are also telltale signs of a car that may potentially need a spark plug replacement early, such as:
- Rough idle
- Engine misfiring
- Problems starting your engine
Consider that this list is absolutely not comprehensive, and these problems on their own do not definitively point to the spark plugs being the solitary culprit. However, the best way to prevent any issues with your vehicle is to take care of it with routine maintenance, and you are definitely doing so with the responsible decision to replace your Subaru Impreza’s spark plugs on a regular basis.
Changing spark plugs on a 2008 Subaru Impreza
This is a process you should be able to do on your own with some commonplace garage tools. Of course, consult your owner’s manual, as well as a factory service manual (FSM for short) or an equivalent Haynes or Chiltons manual. The video shown below does a good job of outlining the process.
Helpful Tools
- A spark plug gap tool. This allows you to check the gap of your spark plugs and increase or decrease it if necessary. Most plugs will come pregapped, but if this is not the case, you should absolutely have one of these.
- I also highly recommend you have a feeler gauge as it makes it a bit easier to check the exact gap, and it comes in handy for a decent number of other jobs.
- A set of spark plug sockets – These come in very handy because many standard sockets are not deep enough for spark plugs. Also, some spark plug holes are a bit smaller, so it requires a thinner wall like the one featured in the product here to fit. The linked product also features a magnet to keep a good hold of the spark plug so you do not drop it into your engine bay!
- A spark plug tester – this is definitely a niche tool, but it can save you a ton of time. Although we’ve discussed spark plug replacement being a good thing to replace regularly and not just when issues occur, you may also be replacing your spark plugs because of a problem. This tool can help you diagnose the exact problem.
- A torque wrench is a very important tool to have in your toolbox. You will want to check your factory service manual to determine the correct torque rating to use when inserting the new spark plugs for your 2008 Subaru Impreza to be confident they are installed properly.
Tips for changing spark plugs on your 2008 Subaru Impreza
- One of the most important things to remember is to avoid overtightening the plugs or worse, cracking them due to overtightenting. Use a torque wrench capable of lower, more precise torque ratings to be sure that you don’t make this mistake.
- You might consider using dielectric grease when installing new spark plugs. You can apply a a small dab to the inside of the boot and the ceramic part of your spark plugs. It prevents voltage leak and helps avoid the misfortune of the boot fusing to the spark plug over time.
- Before starting, remove the negative terminal of your battery. You should always disconnect the battery anytime you work on the electrical system of your Subaru Impreza or any other vehicle.
- Note that this is not official advice as many spark plug manufacturers advise against the use of anti-seize. However, I have heard from numerous old-school mechanics that they always apply a tiny amount of anti-seize to the threads of their spark plugs, especially on older vehicles.
- You should replace spark plugs on a cold engine. Wait at least 30 minutes after your engine has been running before attempting to replace the spark plugs on your 2008 Subaru Impreza