What size socket wrench do you need for an oil drain plug?

By: HowStuffWorks.com Contributors  | 
A socket wrench in different sizes.
A socket wrench is an essential tool in your toolbox. RASimon / Getty Images

A socket wrench is a tool used to grip the head of a fastener such as a nut or bolt to tighten or loosen it. It comes with a long handle to which different size sockets can be attached for tightening different size fasteners. Sometimes the socket wrench has a ratchet handle, allowing the wrench to turn continuously without having to lift up the tool. For each particular job, it's important to choose the size socket wrench that corresponds with the particular hardware.

There are four common socket sizes: 1/4 inch (0.6 centimeters), 3/8 inch (0.9 centimeters), 1/2 inch (1.3 centimeters) and 3/4 inch (1.9 centimeters). In addition, sockets are available in various shapes to fit the different bolt heads: six points (hexagon), eight points (double square), and 12 points (double hexagon). If you choose a socket that's too large, you could damage the tool and injure your hands. Furthermore, some socket wrenches are deeper than normal to allow for bolts that protrude.


Before embarking on a project, for instance replacing your car's engine oil, you need to decide which size socket wrench to use. You need a socket wrench to open the oil drain plug so the used oil can drain from the engine. First, turn on the car to warm up the engine. This thins the oil, allowing it to drain smoothly. Then turn off the engine, firmly set the parking brake and place jack stands under the car. Next, locate the drain plug under the car; it should still be warm from the heated engine. Place a 3/8-inch (0.9 centimeters) socket in the socket wrench, fit it over the drain plug's nut and turn it counterclockwise. The oil drain plug should open easily, draining the used oil from the engine. Make sure to place a bucket and some newspaper under the car's engine to catch all the draining oil.

Oil Drain Plug FAQ

Are oil drain plugs universal?
There is no such thing as a universal oil drain plug. However, the industry uses a few standard sizes that are widely available.
What do I do if my oil drain plug is stripped?
In many ways, it’s safer to replace it since a stripped drain plug could ultimately ruin your engine if left unattended. However, you can also apply welding such as JB Weld to the threads of the drain plug, it's opening and both sides of the attached gasket to seal it in the meantime.
When should you replace the oil drain plug?
Although oil drain plugs are very durable and designed to last for several years, they may have to be changed if they are stripped or they start leaking.
How much does it cost to replace an oil drain plug?
Oil drain plugs generally cost between $100 to $350 depending on where you live. The part itself is quite inexpensive, though the labor for the replacement is extensive.