Changing your own oil is a great way to save money and get to know your car better. For Subaru Impreza owners, that means understanding the basics, and knowing the correct drain plug size is absolutely crucial. Using the wrong size can lead to stripped threads, leaks, and a whole lot of frustration. Let's dive into the specifics so you can confidently tackle your next oil change.
So, What's the Magic Number? Unveiling the Drain Plug Size
Okay, let's get straight to the point. The standard drain plug size for most Subaru Imprezas is 17mm. However, there's a slight twist! While 17mm is the most common size, it's always best to double-check the specific year and model of your Impreza, as there can be slight variations.
Why the potential variation? Subaru, like all manufacturers, sometimes makes small changes over the years. While the core engine design might stay the same, things like drain plug materials or even slight thread pitch adjustments can occur. Therefore, assuming it's always 17mm is a recipe for potential trouble.
Digging Deeper: Year-by-Year Considerations
While a 17mm wrench or socket will usually do the trick, let's break down the nuances by generation to give you the most accurate information possible.
- First Generation (1993-2001): These Imprezas almost universally use a 17mm drain plug. You're likely safe with this size.
- Second Generation (2002-2007): Again, 17mm is the prevalent size. However, it's always wise to give it a quick visual confirmation before you start.
- Third Generation (2008-2011): The 17mm drain plug remains the standard for this generation.
- Fourth Generation (2012-2016): You guessed it, 17mm is still the most common size.
- Fifth Generation (2017-Present): While 17mm is still largely used, it's especially important to confirm the size for these newer models. Small changes are more likely in recent years.
Pro Tip: The best way to be absolutely certain is to look at the drain plug itself. If you can safely access it, take a peek and visually confirm the size before you start loosening anything.
Beyond Size: Understanding Thread Pitch and Material
Knowing the size of the wrench needed is only half the battle. The thread pitch and material of the drain plug are equally important for preventing leaks and damage.
- Thread Pitch: This refers to the spacing between the threads on the drain plug. While the size of the plug refers to the head, the thread pitch determines how tightly it screws into the oil pan. Using a drain plug with the wrong thread pitch can quickly strip the threads in your oil pan, leading to a very expensive repair. Subaru drain plugs typically have a metric thread pitch. Unfortunately, the exact pitch varies and is difficult to determine without specialized tools. This is why it's always best to use an OEM (Original Equipment Manufacturer) drain plug or a high-quality aftermarket replacement specifically designed for your Impreza.
- Material: Most Subaru drain plugs are made of steel. However, the sealing washer (more on that later) can be made of aluminum or copper. The material is important because it affects how tightly you can torque the plug without damaging it.
The Sealing Washer: A Small Part with a Big Job
Don't underestimate the importance of the sealing washer! This small, often overlooked part sits between the drain plug and the oil pan, creating a tight seal to prevent leaks.
- Why it Matters: The sealing washer is designed to crush slightly when the drain plug is tightened, filling any imperfections in the mating surfaces. Reusing an old sealing washer can lead to leaks because it's already been crushed and may not provide a proper seal.
- When to Replace: Always replace the sealing washer every time you change your oil. It's a cheap part, and it's not worth risking a leak to save a few cents.
- Types of Washers: Subaru uses both aluminum and copper sealing washers. Check your owner's manual or a parts catalog to determine the correct type for your Impreza.
Torque Specs: Tighten It Right!
Over-tightening or under-tightening the drain plug is a common mistake that can lead to problems. Using a torque wrench to tighten the drain plug to the manufacturer's specifications is crucial.
- Why Torque Matters: Over-tightening can strip the threads in the oil pan, while under-tightening can cause leaks.
- Finding the Right Torque Spec: The correct torque specification for your Impreza's drain plug can be found in your owner's manual or a repair manual. It's usually around 30-35 ft-lbs (41-47 Nm), but always verify the specific value for your model year.
- Using a Torque Wrench: A torque wrench is a specialized tool that allows you to tighten fasteners to a specific torque value. If you're serious about DIY car maintenance, a torque wrench is a worthwhile investment.
What Happens if You Strip the Drain Plug Threads?
Stripping the drain plug threads is a common and frustrating problem. Here's what you need to know:
- How it Happens: Over-tightening the drain plug is the most common cause of stripped threads. Using the wrong size wrench or socket can also contribute.
- The Consequences: Stripped threads mean the drain plug won't tighten properly, leading to oil leaks.
- Fixing Stripped Threads: There are several ways to fix stripped drain plug threads, ranging from simple to complex:
- Oversized Drain Plug: This is a relatively easy fix that involves installing a drain plug with slightly larger threads.
- Thread Repair Kit (e.g., Helicoil): These kits allow you to repair the existing threads in the oil pan.
- Oil Pan Replacement: This is the most expensive and time-consuming option, but it may be necessary if the threads are severely damaged.
Important: If you're not comfortable repairing stripped drain plug threads yourself, it's best to take your car to a professional mechanic.
Alternative Drain Plugs: Fumoto Valves and Magnetic Plugs
Beyond the standard drain plug, there are a couple of popular alternatives:
- Fumoto Valves: These valves replace the standard drain plug and allow you to drain the oil without using any tools. They're convenient and can help prevent stripped threads.
- Magnetic Drain Plugs: These plugs have a magnet on the end that attracts metal particles in the oil. This can help to remove harmful debris from the engine.
If you're considering either of these options, make sure to choose a high-quality product that's specifically designed for your Subaru Impreza.
Frequently Asked Questions
Q: What size wrench do I need for my Subaru Impreza drain plug?
A: The most common size is 17mm, but always double-check the specific year and model of your Impreza to be sure.
Q: Do I need to replace the sealing washer every time I change my oil?
A: Yes, always replace the sealing washer to ensure a proper seal and prevent leaks.
Q: What happens if I over-tighten the drain plug?
A: Over-tightening can strip the threads in the oil pan, leading to leaks and potentially expensive repairs.
Q: Where can I find the correct torque specification for my drain plug?
A: The torque specification can be found in your owner's manual or a repair manual.
Q: What is a Fumoto valve?
A: A Fumoto valve replaces the standard drain plug and allows you to drain the oil without using any tools, making oil changes cleaner and easier.
Conclusion
Knowing the correct drain plug size and the importance of related components like the sealing washer and torque specs is essential for a successful DIY oil change on your Subaru Impreza. Always double-check the specific requirements for your vehicle year and model to avoid costly mistakes and ensure optimal engine health.