Crush Washer vs Lock Washer: Which One Should You Buy?
A crush washer seals a drain plug by deforming under torque, while a lock washer resists loosening on a bolted joint, and this guide explains the difference.
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An oil change ends with a drain plug, a washer and a choice that looks small until the plug weeps: crush washer vs lock washer is the question, and the answer depends on the job the washer must do. A crush washer seals by deforming under torque, and on an oil drain plug a fresh washer at each oil change keeps the seal honest. A lock washer resists loosening on a bolted joint and is not a seal. The sections below explain each washer, then rank the crush washer listings in the gear section.
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Crush washer vs lock washer: what each washer does
A crush washer is a soft sealing ring that sits between a drain plug and the surface around the drain hole. When the plug is tightened, the washer deforms and fills small surface gaps, which closes the path oil could leak through. The AUTOMAJOR listing describes that action: aluminum washers deform under torque to fill microscopic surface imperfections between the drain plug and oil pan. The same listing notes that Honda recommends replacing the gasket at every oil change, and warns that reusing an old crush washer is a common cause of oil drips and leaks after service.
A lock washer works in a different way. It sits under a bolt head or a nut on a bolted joint and adds grip that resists loosening when vibration tries to turn the fastener. It does not deform into a seal, and it does not close a fluid path. Put a lock washer on a drain plug and the plug may stay tight while oil still finds a path past the joint, because nothing in the joint was shaped to seal.
| Washer | How it works | Where it fits | Reuse |
|---|---|---|---|
| Crush washer | Deforms under torque to fill surface gaps and seal | Oil drain plugs and other sealing joints | Replace at each oil change on a drain plug |
| Lock washer | Adds grip that resists loosening on a bolted joint | Bolted joints that face vibration | Not a seal, so never a substitute for a crush washer |
When a crush washer fits
A crush washer fits wherever a fluid must stay behind a plug or a fitting. The oil drain plug is the classic job: the plug closes the pan, the washer seals the gap, and a fresh washer at each oil change keeps the seal honest. The maierke listing extends the same idea to oil pipes and hydraulic joints. The AKOSN listing names automotive, plumbing and machinery uses for its copper sealing washers.
Material matters for the seal. The AUTOMAJOR listing uses high-purity aluminum, which it describes as flexible, corrosion resistant and resistant to degradation from synthetic and conventional engine oils, and notes that aluminum does not rust. The maierke listing also uses aluminum and describes it as corrosion resistant and oxidation resistant. The AKOSN listing uses copper, which it describes as heat resistant and anti-corrosion. Check the vehicle manual for the washer material and size the maker specifies.
When a lock washer fits
A lock washer fits a bolted joint that must stay tight under vibration. Brackets, guards, mounts and assemblies that shake or cycle with heat are the kind of joints where a fastener that resists backing off is used. In those jobs the washer never needs to hold fluid, so a locking washer adds the grip the joint needs.
The lock washer does not fit a drain plug. A drain plug job is a sealing job, and the seal comes from a washer that deforms into the gap. A lock washer grips to resist turning, but grip alone leaves the fluid path open. If a drain plug weeps after service, check the sealing washer: a reused crush washer, a washer of the wrong size, or a washer made for a different plug.
Choosing between a crush washer and a lock washer
Start from the job, not from the parts bin. If fluid must stay in, choose a crush washer. If a bolt must stay tight, choose a lock washer. If a job needs both sealing and locking, treat them as separate problems and solve each with its own part, rather than asking a single washer to do work it was not shaped for.
Then match the crush washer to the plug. The listings in the gear section cover different sizes, materials and pack counts, so check the drain plug size, the washer material and the part number in the vehicle manual before ordering. For the torque figure, the AUTOMAJOR listing states a Honda specification of 29 ft-lbs (39 Nm) for its 14mm washer, and the best torque wrench for car maintenance guide helps keep that figure honest. The listing warns against overtightening to avoid stripping aluminum oil pan threads.
The gear: crush washer listings ranked
The listings below are ranked for an oil drain job: an exact drain plug fit and stated figures first, then breadth of sizes. No lock washer listing appears in the data for this guide, so the gear section ranks crush washers only.
AUTOMAJOR 20-pack, 14mm aluminum. This listing ranks highest because it gives the fullest set of figures for a drain plug job: dimensions of 14.2mm / 0.56in ID, 20mm / 0.79in OD and 2mm / 0.08in thickness, a 20-pack described as enough for 20 oil changes, and a stated torque figure of 29 ft-lbs (39 Nm). It is a direct replacement for Honda and Acura OEM 94109-14000, and it states the single-use rule plainly: Honda recommends replacing the gasket at every oil change. The listing also notes that the washers suit standard 5,000-mile intervals. Its weakness is breadth: it covers a single size.
Honda OEM 10-pack, 14mm. This listing ranks next because it is the genuine OEM part itself: Honda OEM 94109-14000 oil crush washers in a 10-pack, described as OEM Honda made in Japan, with spec table dimensions of 0.87 Inches x 0.87 Inches x 0.08 Inches. Its weakness is a thin listing: the bullets repeat the title rather than stating material, a torque figure or a use note, so a buyer must lean on the part number and the spec table alone.
maierke assortment, 510 pieces, 18 sizes. This listing ranks next for breadth: a 510-piece aluminum assortment in 18 sizes from M6 to M24, packed in a labeled plastic box for size identification. The listing gives the count for each size, from M6 with 145 pieces down to M24 with 5 pieces. The listing describes aluminum as corrosion resistant and oxidation resistant and names oil drain plugs, oil pipes and hydraulic joints as uses. Its weakness is depth: it gives no per-size dimensions and no torque figure, so the manual still decides the size for a given plug.
AKOSN copper assortment, 120 pieces, 15 sizes. This listing ranks last for oil drain work because it states no per-size dimensions, no torque figure and no part number cross-reference, even though its breadth is real: 120 copper pieces in 15 sizes from M5 to M24, in a clear labeled case, with listed dimensions of 5.35 inches x 3.81 inches x 0.7 inches. Copper suits sealing work and the listing names automotive, plumbing and machinery uses, but it gives no per-size dimensions, no torque figure and no part number cross-reference. For a garage that needs copper specifically, it remains a usable assortment; for a drain plug job that needs a stated size and torque figure, the listings above it state more.
For a wider look at kits, see the best crush washer kit for oil changes guide, and for drain plug alternatives see the oil drain valve vs oil drain pan guide.
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FAQ: garage tools
What are crush washers?
A crush washer is a soft sealing ring, usually aluminum or copper, that deforms under torque to fill small gaps between a drain plug and the surface around it. That deformation is the seal. Because the seal comes from deforming, the AUTOMAJOR listing calls its washer single-use: Honda recommends replacing the gasket at every oil change rather than reusing it.
Can you stack crush washers?
The listings do not describe stacking. The AUTOMAJOR listing describes a single fresh washer at each oil change, and warns that reuse is a common cause of drips after service. Use a single washer of the size the manual specifies.
Aluminum or copper crush washer?
Check the manual for the plug in question. The AUTOMAJOR and maierke listings use aluminum, which they describe as corrosion resistant, and the AUTOMAJOR listing notes that aluminum does not rust and resists degradation from synthetic and conventional engine oils. The AKOSN listing uses copper, which it describes as heat resistant and anti-corrosion.
What size crush washer for a transmission drain plug?
Not stated in these listings, which cover oil drain plugs and general sealing uses, with sizes from M5 to M24 across the assortments and a 14mm washer in the single-size listings. Check the vehicle manual for a transmission drain plug rather than guessing from an oil drain size.
Can you reuse a crush washer?
In effect, no: a crush washer seals by deforming, and the AUTOMAJOR listing states that Honda recommends replacing the gasket at every oil change. Keep a fresh washer on hand for each oil change.
Related: the engine and shop equipment hub, the best crush washer kit for oil changes guide and the best torque wrench for car maintenance guide.
