Knowing the correct oil drain plug size helps you choose the right replacement plug or the proper socket or wrench for installation. Most Briggs & Stratton engines use standard pipe or square-drive plugs that thread into the crankcase and seal the oil reservoir. The size and thread type depend on the engine series and model.
Briggs and Stratton Oil Drain Plug Size
| Engine Series / Example Model Group | Plug Part # | Drive / Head Type | Thread Size / Type | Typical Fit Notes |
|---|---|---|---|---|
| Flathead & Performance (Animal, LO206, World Formula, Raptor, Model 12, 13, 19) | 691686 | Square / OEM plug | 1/4-18 NPTF | Common on flathead and OHV engines, including racing and performance models |
| Classic Small Engine Series (192, 194, 195, etc., older horizontal-shaft) | 690946 (superseded by 805048, replaces 94239, 91084) | Square / OEM plug | 3/8-18 NPT | Fits many older horizontal-shaft engines, standard small engine drain |
| Mid-range Briggs engines (090000 and 100000 series, Intek V-Twin) | 691680 | Square / 3/8″ socket drive, recessed square | 3/8-18 NPTF, ~1/2″ | Typical OEM plug for mid-range engines, including Intek V-Twin models |
| Small engines needing magnetic plug (2–5 HP engines, 7-11 Gross HP horizontal) | RT_9965 or 690289 (magnetic) | Hex head magnetic | 1/4-18 NPT or 3/8-18 NPTF | Magnetic plug option for small to mid HP engines, collects metal particles |
| Older push mower engines (small horizontal crankshaft, 5 HP and under) | 690946 / 805048 or 492030, 691663 | Square head | 1/4-18 NPTF, 1/4″ I.D. Dia. | Often used on older lawn mower engines, 5 Gross HP horizontal crankshaft |
| Engines above 5 HP (horizontal crankshaft) | 492031 | Square / OEM plug | 3/8-18 NPTF, 1/2″ I.D. Dia. | For higher HP horizontal shaft engines |
| 2-cylinder liquid-cooled Vanguard (540000 & 610000 series) | 807392 or 555578 (oversize) | Hex head (18mm for oversize) | M14 x 1.5 | For liquid-cooled Vanguard twins, oversize option available |
| Vanguard Twin (V-Twin Vanguard, except liquid-cooled) | 690946 or 5401H valve | Square / OEM plug | 3/8-18 NPTF | For air-cooled Vanguard twin-cylinder engines |
| Small engines (general, with NPT-1/4 plug) | EZ-115 or compatible | Various (valve options) | 1/4-18 NPT | General small engines, EZ drain valve replacement |
| Small engines (general, with NPT-3/8 plug) | EZ-110 or compatible | Various (valve options) | 3/8-18 NPT | General small to mid engines, EZ drain valve |
| Large engines (general, with NPT-1/2 plug) | EZ-202 or compatible | Various (valve options) | 1/2-14 NPT | For larger Briggs & Stratton engines |
| 13.5 XR Engine (used in mini excavators, Chinese models like FF12) | EZ-109 or standard | Bolt head | M12 x 1.5 | Common in applications like mini excavators, metric thread |
| Model 401417 (older engine) | 751-3001 | Unknown | Unknown | Specific to model 401417, check manual for details |
| Small gasoline engines (magnetic option) | 690289 | Square / OEM plug | 3/8-18 NPTF | Genuine magnetic drain plug for small engines |
| General older models (replaces 93418) | 93418 replacement | Square head | Small size (0.9 x 0.9 x 0.7 inches) | For various small engines, ensure compatibility |
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What is an Oil Drain Plug?
An oil drain plug is a threaded fastener that seals the oil drain hole in the engine’s crankcase. It allows for easy draining of old oil during maintenance. The plug can be:
- Square head – removed with a ratchet or square socket
- Hex head – removed with a wrench or socket
- Magnetic plug – collects metal particles for better oil cleanliness
Finding the Plug on Your Engine
On most horizontal-shaft Briggs & Stratton engines, the drain plug is located on the bottom side of the engine block near the crankshaft. On vertical-shaft engines, it may be on the side or near the oil fill and dipstick area.
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How to Identify the Correct Drain Plug for Your Engine
Briggs & Stratton models vary, so it is important to:
1. Find Your Engine Model, Type, and Code
This information is printed on a label on the engine, often near the shroud, muffler, or crankcase. It usually includes:
- Model number
- Type number
- Code number
These codes together allow you to identify the exact parts your engine uses.
2. Use a Parts Diagram or Lookup
Parts diagrams or official engine manuals show the oil drain plug part and its specifications, including thread type and size.
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Common Plug Sizes and Tools
Square-Drive Drain Plugs
- Common on older and mid-tier engines
- Removed with a 3/8″ or 1/2″ square ratchet or socket
- Examples include OEM plugs 690946 and 805048
Pipe Thread Drain Plugs
- Often specified in NPTF sizes, such as 1/2″ diameter with 3/8-18 thread
- Smaller engines may use 1/4″ pipe thread for magnetic plugs
Magnetic Drain Plugs
- Replaces the OEM plug with a magnetic fitting
- Collects metal shavings to extend engine life
- Commonly 1/4″ pipe thread for 2–5 HP engines
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How to Measure Your Existing Plug
- Remove the drain plug carefully.
- Measure the thread pitch and diameter using a thread gauge or take it to a parts store.
- Match it to an NPTF chart. Common sizes for small engines are 1/4″ and 1/2″ NPTF.
Why Plug Size Matters
Using the wrong oil drain plug can result in:
- Oil leaks due to improper sealing
- Stripped threads in the crankcase
- Difficulty during future oil changes
Always use the correct OEM-specified plug or an approved replacement.
Maintenance Tips
- Change oil after the first five hours, then every 50 engine hours or annually
- Warm the engine before draining oil to improve flow
- Clean around the drain area to prevent dirt entry
- Tighten the drain plug to the torque specified in the manual, avoiding over-tightening
Final Notes
Briggs & Stratton oil drain plug sizing is not universal. It depends on the engine series and design. To ensure a proper fit:
- Consult the operator’s manual or parts diagram for your engine
- Use the engine model and type code for accurate parts information
- Consider a magnetic drain plug for additional engine protection
