Understanding Oil Crush Washers: A Small Component with a Big Role in Vehicle Maintenance

Oil changes are one of the most essential maintenance tasks for keeping your engine in good health. While many drivers focus on the type of oil or the quality of the oil filter, one small but vital component is often overlooked — the oil crush washer. This inexpensive item plays a key role in preventing oil leaks and ensuring a secure seal at the drain plug. In this article, we’ll take a closer look at what crush washers do, the different types available (including the popular 12mm crush washer), and where you can find replacements such as crush washers at AutoZone.

What Is an Oil Crush Washer and Why Is It Important?

An oil crush washer is a soft metal ring, usually made of copper or aluminum, that sits between your oil drain plug and the oil pan. When the drain plug is tightened, the washer deforms slightly (or “crushes”) to create a tight seal. This prevents oil from seeping out of the pan and ensures your engine retains the proper amount of lubricant.

Despite its small size, a drain plug washer has a significant function. Over time, washers can become compressed, worn, or damaged. If not replaced during routine oil changes, an old or flattened washer can lead to leaks, contamination, or damage to the oil pan threads. Because of its crucial role in sealing the oil drain plug, many manufacturers recommend replacing the washer every time the oil is changed.

Types and Sizes: Understanding the 12mm Crush Washer

Crush washers come in different sizes and materials to suit various engine designs. One of the most common sizes is the 12mm crush washer, often used in Honda, Toyota, and other Japanese vehicles. The “12mm” refers to the inner diameter of the washer, which must match the bolt size of the drain plug.

Materials matter too. Here are the typical options:

Aluminum: Softer and easier to deform, creating a good seal with minimal torque. Often used for aluminum oil pans.

Copper: Durable and highly resistant to corrosion. Ideal for high-heat applications.

Fiber/Nylon: Less common but still used in certain OEM applications, especially in motorcycles or small engines.

Choosing the correct washer size and material is essential. A washer that’s too small won’t fit the drain plug; too large, and it may not seal properly. If you're unsure, consult your vehicle’s owner manual or take the original washer to an auto parts store for comparison.

Replacing and Buying a Drain Plug Crush Washer

Replacing a drain plug crush washer is a simple task that can make a big difference in leak prevention. When changing your oil:

Remove the old washer along with the drain plug.

Inspect the plug threads and oil pan surface for wear.

Install a new oil plug crush washer before tightening the plug.

Some modern vehicles use reusable sealing washers or rubber O-rings integrated into the plug, but most still rely on disposable crush washers. Always confirm which type your car uses.

When it's time to buy a replacement, AutoZone is a convenient place to find crush washers. They carry a range of sizes, including the standard 12mm drain plug washer, and their staff can help identify the correct part for your make and model. You can also purchase crush washers in multi-packs, which can be more economical if you change your oil frequently.

Online retailers, dealership parts departments, and other auto parts stores also stock these washers. Just be sure to get the correct diameter and material for your vehicle.

A new oil filter and fresh oil might be the stars of your engine maintenance routine, but the humble drain plug crush washer plays a supporting role that’s too important to ignore. Whether it’s a 12mm crush washer for your Honda or a copper washer for a high-performance engine, replacing this small part during each oil change can prevent future problems like leaks and costly repairs.

When in doubt, ask your parts provider — including places like AutoZone — for the correct washer. Keeping an extra few on hand is a smart move for any DIY mechanic or car owner who wants to maintain their engine’s health with confidence.