What an oil seal cross reference chart does
An oil seal cross reference chart matches the part number from one manufacturer to the equivalent seals made by other manufacturers. If you have a Timken part number but your supplier stocks SKF, or you need a National seal but only find a Fel-Pro equivalent in stock, a cross reference tells you which seals are dimensionally and functionally identical. The chart lists the original equipment manufacturer (OEM) number, the National Seal Company number, and equivalents from competitors like Timken, SKF, Garlock, and others.
The reason you need this: oil seals are made by dozens of companies, and a single seal design may be sold under five or six different part numbers depending on who manufactured it and who is selling it. A cross reference chart eliminates guessing and ensures you install a seal that matches your engine's exact specifications rather than buying something close and hoping it works.
Key Takeaways
- Oil seal cross reference charts match part numbers across manufacturers so you can find the right seal even if your supplier does not stock the original brand.
- National Seal Company numbers are one standard in the chart, but the seal itself may be identical to a Timken, SKF, or Garlock part with a different number.
- You need three pieces of information to use a chart correctly: the OEM part number, the seal dimensions (bore, outside diameter, width), and the process (engine type and year).
- Online cross reference databases from bearing distributors and seal manufacturers are faster and more current than printed charts, which can become outdated as part numbers change.
- If a cross reference shows multiple equivalents, any of them will work as long as the dimensions and material match your engine's requirements.
How to read a National Seal cross reference chart
A cross reference chart is organized in columns. The first column lists the OEM part number (the number stamped on the original seal or listed in your engine manual). The next column shows the National Seal equivalent. The remaining columns show equivalents from other manufacturers: Timken, SKF, Garlock, Freudenberg, and sometimes others depending on the chart's scope.
To use it, locate your starting part number in the leftmost column. Read across the row to find the National Seal number in the second column. If you need a different brand instead, continue reading across to find that manufacturer's equivalent. All numbers in that row represent the same seal—same bore diameter, outside diameter, width, and material composition.
Some charts also include a dimensions column showing bore × OD × width in millimeters. This is your safety check: if you find a part number but the dimensions do not match what your engine requires, that row is not the right seal. Dimensions are the truth; part numbers can vary by region or supplier.
Where to find National Seal cross reference data
The National Seal Company publishes cross reference information through bearing and seal distributors rather than a single public database. Major distributors like Anixter, Motion Industries, and Wesco carry National Seal products and often provide cross reference tools on their websites. You enter a part number and the system shows you equivalents in stock or available through their network.
Bearing supply companies like SKF, Timken, and FAG also maintain cross reference databases because they compete directly with National Seal. Their online tools let you search by OEM number, dimensions, or process. These databases are updated regularly as manufacturers discontinue old part numbers and introduce new ones.
If you are working on a specific engine, the engine manufacturer's parts catalog (available from dealers or online) lists the OEM seal number and sometimes cross references to aftermarket equivalents. For example, a Ford engine manual will show the Ford part number and may cross-reference it to National, Timken, or other brands that Ford approves for replacement.
Understanding seal dimensions and material codes
Oil seals are specified by three dimensions: bore (the inner diameter that contacts the shaft), outside diameter (OD, the outer edge that sits in the housing), and width (the axial thickness). These are always measured in millimeters on modern seals. A seal marked 40 × 62 × 10 has a 40 mm bore, 62 mm OD, and 10 mm width. If any dimension is wrong, the seal will not seat properly and will leak.
The material code tells you what the seal is made of. Most oil seals use nitrile rubber (NBR), which resists mineral oil and temperatures up to about 100°C. Some engines require fluorocarbon (FKM or Viton), which handles higher temperatures and synthetic oils. A cross reference chart may show the material in parentheses or as a suffix. If your engine originally used FKM and you install NBR, the seal may swell or harden prematurely and fail.
When you cross reference a part, always verify that the material matches. If the chart shows multiple equivalents but one is NBR and another is FKM, they are not interchangeable even though the dimensions are identical. Your engine's manual or the original seal's markings will tell you which material is correct.
Using cross references for common engine applications
For automotive engines, the OEM number is usually found in the factory service manual under "Crankshaft Seals" or "Engine Seals." Domestic engines (Ford, Chevrolet, Dodge) often use National Seal or Timken as OEM suppliers, so cross references between these two are usually direct and reliable. Import engines (Toyota, Honda, Nissan) may use different suppliers, and cross references can be less straightforward because fewer aftermarket companies stock equivalents.
Industrial engines and pumps often have multiple seal suppliers because they are produced in higher volumes and over longer periods. A 1990s Caterpillar engine seal may have been made by National, but a 2010 equivalent might be sourced from SKF or Garlock. Cross reference charts for industrial equipment are often more detailed and include process notes because the same seal bore size can be used in different ways (crankshaft, camshaft, pump shaft) and requires different materials.
Marine and small engine applications (outboards, generators, lawn equipment) sometimes have limited cross reference data because these engines are produced by many manufacturers and volumes are lower. In these cases, contacting the engine maker directly or a specialized distributor for that engine type is often faster than searching a general chart.
When a cross reference is incomplete or unavailable
If you cannot find a cross reference for your part number, the seal may be obsolete, region-specific, or made by a manufacturer no longer in business. Start by confirming the part number is correct—check the original seal itself, the engine manual, and the parts diagram. A single digit error will send you to the wrong seal.
If the number is correct but no cross reference exists, contact the engine or equipment manufacturer's parts department with the OEM number and ask for the current equivalent. Many manufacturers have upgraded seals over time and can tell you what to use as a replacement. You can also provide the seal dimensions to a bearing distributor and ask them to find a match in their inventory by size and material rather than by part number.
As a last resort, if the seal is truly unique and no equivalent exists, you may need to order it directly from the original manufacturer or through a specialty distributor. This is rare for common engines but more common for older, discontinued, or specialized equipment.
Frequently Asked Questions
Can I use any seal with the same dimensions as long as the bore and OD match?
Not always. Dimensions must match, but so must the material and the seal type (single lip, double lip, cassette). A seal with the correct bore and OD but the wrong material or lip configuration will leak or fail prematurely. Always verify the material code and seal design match the original before substituting.
What if the cross reference shows multiple National Seal numbers for one OEM part?
This usually means the seal was redesigned or the part number was updated, but both versions are still available. Either one will work in your process. Check the dimensions to confirm they are identical, and use whichever is in stock or cheaper. The newer number is often preferred because it reflects current manufacturing standards.
Do I need to cross reference if I am buying from the same brand as the original?
No. If your engine originally used a National Seal and you are buying a National Seal replacement with the same part number, no cross reference is needed. Cross references are only necessary when you are switching brands or when the original part number is no longer available.
Are online cross reference tools more accurate than printed charts?
Yes, generally. Online databases are updated as manufacturers change part numbers and discontinue old products. Printed charts can become outdated within a year or two. Use an online tool from a major distributor or the seal manufacturer whenever possible, and verify the dimensions match your requirements before ordering.