What size is the drain plug on a LS oil pan?
Most GM LS engines use a 1/2-20 UNF drain plug with a 14mm hex head. Some variants or aftermarket pans may use metric M14x1.5 threads, so verify the exact specification for your model and year.
Overview of typical drain plug sizes on LS engines
The following sizes cover what you’re most likely to encounter when servicing LS oil pans. Variations exist, especially with aftermarket pans or limited-run models, so always double-check your specific vehicle.
- 1/2-20 UNF thread with a 14mm hex head — the standard factory configuration on most LS V8 engines.
- M14x1.5 thread — seen on some aftermarket pans or select models; may use a metric sealing approach.
Knowing these general possibilities helps you source the correct replacement drain plug and avoid cross-threading or leaks during service.
How to confirm the exact size on your LS oil pan
To ensure you get the correct plug for your vehicle, use one or more of these verification methods:
- Consult the vehicle’s service manual or GM parts catalog for your exact year/model; documentation lists the drain plug thread size and head type.
- Inspect the current drain plug: measure the thread diameter with calipers and check the pitch, or compare the plug to a thread gauge.
- Ask a GM dealer or a knowledgeable shop with your VIN on hand; some LS variants have unique drain plug specs.
Accurate verification reduces the risk of cross-threading, leaks, or the wrong sealing washer when you replace the plug.
Practical guidance for changing or replacing the drain plug
When you’re replacing the drain plug, follow these practical steps to ensure a proper seal and long life:
- Use the correct torque specification from your service manual to avoid over-tightening or stripping the pan threads.
- Install the appropriate sealing component—most LS plugs use a crush washer or gasket; replace with a new one if required by the plug design.
- Clean the area, install the new plug straight, and monitor for leaks after re-filling with oil.
The takeaway: while the most common drain plug size on LS engines is 1/2-20 UNF with a 14mm head, always verify for your specific model and year, especially if you’re using aftermarket pans or parts.
Summary
For the GM LS family, the standard drain plug is typically 1/2-20 UNF with a 14mm hex head. Some aftermarket pans or particular models may use metric M14x1.5 threads. Always confirm with your exact vehicle’s manual or by inspecting the current plug, and follow proper torque and sealing guidelines when replacing it.
