Oil Pan Drain Plug Size Guide
How to read oil pan drain plug sizes, find the size your engine needs, match the washer, and deal with damaged threads without guessing.
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An oil change stalls at the drain plug when the plug in hand does not match the hole in the pan. The thread has to match, the washer has to match, and the plug has to seat without forcing it. That match is the oil pan drain plug size: the thread size of the plug that fits the drain hole in your oil pan, written as a diameter and a pitch. The washer that seals it has to match the plug too. Get the size right and the plug threads in by hand, seats flat, and holds oil. Get it wrong and the plug cross-threads, strips the pan, or weeps oil onto the floor.
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Below: how plug sizes are written, how to find the size for your vehicle, how to match the washer, and what to do when the threads are damaged.
Oil pan drain plug size: how the size is written
A metric drain plug size reads as a thread diameter and a pitch. M12-1.75 is a plug with a 12 mm thread diameter and a 1.75 pitch, while M12-1.25 is the same diameter with a finer pitch, so the plugs do not interchange even though the diameter matches. Dorman lists the M12-1.75 plug as part 65430 with a 15 mm head size, and the M12-1.25 plug as part 090-038CD with a 14 mm head size. The head size is the wrench size for the plug head, not the thread size, so a plug that takes the same wrench can still have a different thread.
Washer and repair kits show the range of sizes on the road. Washer kits list gasket sizes from M6 to M24: M6, M8, M10, M12, M14, M16, M18, M20, M22 and M24. Repair taps run from M13 to M22: M13 x 1.25, M13 x 1.5, M15 x 1.5, M17 x 1.5, M20 x 1.5 and M22 x 1.5. SAE sizes appear beside metric sizes in mixed kits, with 1/2 inch plugs listed for GM, Ford and Chrysler applications in the ABN 76-piece assortment, which also lists 12mm x 1.25, 12mm x 1.75, 14mm x 1.5, 18mm x 1.5 and 20mm x 1.5 plugs.
| Size | Example listing | Notes |
|---|---|---|
| M12-1.75 | Dorman 65430 | Head size 15 mm |
| M12-1.25 | Dorman 090-038CD | Head size 14 mm |
| M13 x 1.25, M13 x 1.5, M15 x 1.5, M17 x 1.5, M20 x 1.5, M22 x 1.5 | BILITOOLS and Luney repair kits | Tap sizes for damaged threads |
| 1/2 inch, 12mm x 1.25, 12mm x 1.75, 14mm x 1.5, 18mm x 1.5, 20mm x 1.5 | ABN 76-piece assortment | SAE and metric plugs in a mixed kit |
| M6 to M24 | maierke and Ruibapa washer kits | Washer sizes, not plug sizes |
How to find your oil pan drain plug size
The size lives in the service manual, in the listing for a replacement plug, or in the pan threads. Work through the checks in order and stop at the match that fits by hand.
- Check the service manual. The service manual lists the drain plug size for the engine, and it is the match to trust over a parts-store guess.
- Read the old plug. The size shows in the listing for the replacement plug, as with the Dorman 65430 at M12-1.75 and the Dorman 090-038CD at M12-1.25.
- Measure the thread. A caliper across the threads gives the diameter, and a thread pitch gauge gives the pitch; compare the readings against the sizes in the table above.
- Use the fitment check on the listing. Dorman listings ask for the vehicle in the garage tool and show a Confirmed Fit bar, with a note where more verification is needed.
- Match the washer to the plug. A washer sized for M12 will not seal a plug sized for M14, so check the washer size against the plug size before the plug goes in.
Crush washers: match the washer to the plug
Many drain plugs seal with a crush washer, a flat ring that deforms as the plug tightens and fills the gap between the plug head and the pan. A washer from the wrong size will not seat flat, and a used washer that has already deformed will not seal the same way again, so a fresh washer sized to the plug is part of the job.
Washer kits cover the common range. The maierke 1160-piece kit lists 18 sizes from M6 to M24, with 489 copper washers and 671 aluminum washers, and the Ruibapa 1160-piece kit lists the same 18 sizes with 580 copper washers and 580 aluminum washers. The Dsnaduo 100-piece kit covers 12 sizes, and the Dsnaduo 330-piece kit covers 36 sizes, with gasket sizes listed down to the millimeter, such as 24.7×11.5mm and 20.3×11.8mm. Ruibapa lists its gaskets at 1-2mm thick. Pick the washer that matches the plug thread, not the washer that looks close.
When the drain plug threads are damaged
A plug that will not thread in by hand, or a pan that weeps oil around a plug that felt tight, points to damaged threads in the pan. A repair kit cuts a larger thread in the pan and supplies a larger plug to match it, so the pan keeps a working drain hole.
The BILITOOLS 84-piece repair kit carries 6 taps in M13 x 1.25, M13 x 1.5, M15 x 1.5, M17 x 1.5, M20 x 1.5 and M22 x 1.5, with 18 sump plugs, 30 copper washers and 30 aluminum washers to suit the tap sizes. The Luney 114-piece kit carries the same 6 tap sizes with 36 plugs and 72 washers. The kits list taps for passenger cars and light trucks, so check the tap size against the plug size the pan needs before cutting a larger thread.
What to check before the plug goes back in
- Thread the plug in by hand. If it binds or cocks to the side, back it out and check the threads instead of forcing it.
- Fit a fresh washer. The washer seats between the plug head and the pan, and a washer from the wrong size will not seal.
- Follow the service manual for tightness. The service manual gives the tightening spec for the plug, and a plug tightened past that spec can strip the pan threads.
- Check for weeping after the oil goes in. A dry pan after the first start means the plug and washer seated; a wet pan means the plug comes out and the washer and threads get checked again.
- Keep the old plug as a reference. Its threads match the size the pan needs, and it saves another trip when the replacement plug in hand is the wrong size.
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FAQ: garage tools
What size is a standard oil drain plug?
There is no standard size that fits every engine. Common metric sizes in the listings run from M12 to M22, with Dorman listing M12-1.75 and M12-1.25 plugs and repair kits listing taps from M13 x 1.25 to M22 x 1.5. The ABN assortment also lists 1/2 inch plugs beside metric sizes. Check the manual for the size your engine needs.
How do I read M12-1.75 on a drain plug?
M12 is the thread diameter in millimeters and 1.75 is the pitch, the spacing between threads. A plug marked M12-1.25 has the same diameter with a finer pitch, so it will not fit a hole cut for M12-1.75. Match the diameter and the pitch, not the diameter alone.
Do I need a new crush washer with every oil change?
A crush washer deforms as it seals, so a washer that has already deformed will not seal the same way again. Washer kits make a fresh washer easy to keep on hand: the maierke 1160-piece kit lists 18 sizes from M6 to M24, so the size for the next oil change is in the box. Fit a fresh washer sized to the plug at each oil change.
Can I use a 1/2 inch plug in a metric oil pan?
No. A 1/2 inch plug has a different thread from a metric plug, and forcing it will damage the threads in the pan. Mixed kits carry SAE and metric sizes side by side for a reason: the ABN 76-piece assortment lists 1/2 inch plugs with 12mm x 1.25, 12mm x 1.75, 14mm x 1.5, 18mm x 1.5 and 20mm x 1.5 plugs, so pick the size that matches the pan, not the size that looks close.
What do I do if the drain plug threads are stripped?
Stop forcing the plug and check the pan threads. A repair kit cuts a larger thread and supplies a matching plug: the BILITOOLS 84-piece kit carries 6 taps from M13 x 1.25 to M22 x 1.5 with 18 sump plugs, and the Luney 114-piece kit carries the same 6 tap sizes with 36 plugs. If the pan threads will not hold a repair plug, a shop can advise on the next step.
Related: how to change oil at home, crush washer kits for oil changes, large oil drain pans, quick connect oil drain plugs and the engine and shop equipment hub.
