Changing your own oil is a fantastic way to save money and get to know your Subaru Impreza better. But before you dive in, you need to know the basics, and that starts with the drain plug. Knowing the correct size and torque specifications is crucial to avoid stripping threads, leaks, and costly repairs. Let's get down to brass tacks and figure out exactly what size drain plug you need, and everything else you should know about it.
Getting Down to Size: The Impreza Drain Plug De-Mystified
So, what's the magic number? For most Subaru Impreza models, the oil drain plug size is a 17mm. This applies to a wide range of model years, from the early 2000s up to the present day. However, it's always a good idea to double-check based on your specific year and engine type, as minor variations can occur.
Why is getting the right size so important? Using the wrong size socket or wrench can lead to rounding off the drain plug's head, making it incredibly difficult to remove. Trust me, you don’t want to be stuck with a stripped drain plug halfway through an oil change. It turns a simple task into a frustrating ordeal.
Why You Can't Just Wing It: The Importance of Correct Torque
Okay, you know the size. Now, let's talk about torque. Torque is the rotational force you apply when tightening the drain plug. Too little torque, and the plug might loosen over time, leading to oil leaks. Too much torque, and you risk stripping the threads in the oil pan - a very expensive mistake to fix.
The recommended torque specification for most Subaru Impreza oil drain plugs is between 25 and 30 ft-lbs (foot-pounds). Again, this is a general guideline, and it's always best to consult your owner's manual or a reliable service manual for the exact specification for your specific model year and engine.
Important Note: Investing in a torque wrench is essential for accurate tightening. Don't rely on guesswork! A torque wrench allows you to apply the precise amount of force needed to secure the drain plug without overtightening.
Gaskets and Crush Washers: Your Leak Prevention Allies
The drain plug doesn't seal directly against the oil pan. Instead, it relies on a crush washer or gasket to create a tight, leak-proof seal. These washers are designed to be single-use items, meaning you should always replace them with a new one each time you change your oil.
Why? Because the washer deforms slightly when tightened, conforming to the surfaces of the drain plug and oil pan. Reusing a crush washer that's already been compressed can lead to leaks, even if you torque the drain plug to the correct specification.
There are typically two main types of washers used on Imprezas:
- Aluminum Crush Washers: These are the most common type. They're inexpensive and provide a good seal.
- Copper Crush Washers: Some Impreza models or aftermarket drain plugs may use copper crush washers. These are also effective at creating a seal.
Make sure you get the correct type and size washer for your drain plug. The inner diameter should match the diameter of the drain plug's threaded portion. A slightly larger outer diameter is acceptable, but it shouldn't be so large that it interferes with the drain plug's seating surface.
Drain Plug Materials: OEM vs. Aftermarket
Subaru's original equipment manufacturer (OEM) drain plugs are typically made of steel. They're durable and reliable, designed to withstand repeated use. However, there are also aftermarket drain plugs available, often made from different materials like:
- Magnetic Drain Plugs: These plugs have a magnet embedded in the tip. The magnet attracts and traps metallic particles circulating in the engine oil, helping to keep the oil cleaner and potentially prolonging engine life. They're a popular upgrade for enthusiasts.
- Aluminum Drain Plugs: While lighter than steel, aluminum drain plugs are generally not recommended. Aluminum is softer than steel and more prone to stripping or damage.
- Stainless Steel Drain Plugs: Some aftermarket options are made from stainless steel. These offer good corrosion resistance but may not be significantly stronger than OEM steel plugs.
If you're considering an aftermarket drain plug, do your research and choose a reputable brand. Magnetic drain plugs can be a worthwhile upgrade, but avoid aluminum plugs unless you have a specific reason to use them.
Dealing with a Stripped Drain Plug: A Worst-Case Scenario
Unfortunately, stripping the drain plug threads is a common problem, especially if the plug has been overtightened in the past. If you find yourself in this situation, don't panic! There are several ways to address it:
- Oversized Drain Plug: This is often the easiest solution. An oversized drain plug has slightly larger threads that can grip the damaged threads in the oil pan.
- Thread Repair Kit: These kits contain a tap to recut the threads in the oil pan and an insert that provides new, undamaged threads for the drain plug. They're a more involved repair but can be very effective.
- Oil Pan Replacement: In severe cases, the oil pan may be so badly damaged that it needs to be replaced. This is the most expensive option and requires more extensive mechanical knowledge.
Prevention is key! Always use a torque wrench, replace the crush washer, and avoid overtightening the drain plug.
Model Year Variations: Why You Should Always Double-Check
While the 17mm size is common for most Imprezas, there can be variations depending on the model year and engine type. For example, some older models or models with different engines might use a different size drain plug.
To ensure you have the correct size, consult your owner's manual, a reliable service manual (like Haynes or Chilton), or a parts catalog specific to your Impreza. You can also measure the drain plug using a caliper.
Pro Tip: When ordering a new drain plug or crush washers, always specify the year, make, and model of your Impreza to ensure you receive the correct parts.
Tools You'll Need for a Smooth Oil Change
Beyond the correct drain plug and crush washer, you'll need a few other essential tools to perform a successful oil change:
- Socket Wrench: To remove and tighten the drain plug. A 17mm socket is the most common size, but double-check based on your Impreza's specifications.
- Torque Wrench: Absolutely essential for tightening the drain plug to the correct specification.
- Oil Filter Wrench: To remove and install the oil filter. The size will vary depending on the oil filter you're using.
- Oil Drain Pan: To catch the old oil.
- Funnel: To pour the new oil into the engine.
- Gloves: To protect your hands.
- Rags or Paper Towels: For cleaning up spills.
- Jack and Jack Stands (Optional): To raise the vehicle for easier access to the drain plug and oil filter. Always use jack stands for safety!
Step-by-Step Guide to Changing Your Oil (Brief Overview)
While a full oil change guide is beyond the scope of this article, here's a quick overview of the process:
- Warm up the engine: Run the engine for a few minutes to warm the oil. Warm oil flows more easily.
- Raise the vehicle (if necessary): Use a jack and jack stands to safely raise the vehicle.
- Locate the drain plug: It's usually on the bottom of the oil pan.
- Position the drain pan: Place the drain pan under the drain plug.
- Remove the drain plug: Use the socket wrench to loosen and remove the drain plug. Be careful, as the oil will be hot.
- Let the oil drain completely: Allow all the old oil to drain out.
- Remove the old oil filter: Use the oil filter wrench to remove the old oil filter.
- Install the new oil filter: Lightly lubricate the oil filter's gasket with fresh oil and screw it on by hand until snug. Then, tighten it another ¾ turn.
- Install the new drain plug: Replace the crush washer and tighten the drain plug to the correct torque specification using a torque wrench.
- Add new oil: Refer to your owner's manual for the correct amount and type of oil.
- Check the oil level: Use the dipstick to check the oil level and add more oil if needed.
- Start the engine: Run the engine for a few minutes and check for leaks around the drain plug and oil filter.
- Dispose of the old oil properly: Take the old oil to a recycling center or auto parts store.
Frequently Asked Questions
- What happens if I overtighten the drain plug? Overtightening can strip the threads in the oil pan, leading to leaks and costly repairs. Always use a torque wrench.
- Can I reuse the crush washer? No, you should always replace the crush washer with a new one each time you change your oil to ensure a leak-proof seal.
- Where can I find the correct torque specification for my Impreza? Consult your owner's manual, a reliable service manual, or a parts catalog specific to your model year and engine.
- Is a magnetic drain plug worth the upgrade? Many enthusiasts believe magnetic drain plugs help prolong engine life by trapping metallic particles in the oil.
- What type of oil should I use in my Impreza? Refer to your owner's manual for the recommended oil type and viscosity for your engine.
The Final Drop: Knowing Your Impreza's Drain Plug
Understanding the size and torque specifications of your Subaru Impreza's drain plug is essential for a successful and trouble-free oil change. Armed with this knowledge, you can confidently tackle this routine maintenance task and keep your Impreza running smoothly for years to come; Remember to always use the correct tools and refer to your owner's manual for specific guidance.