AMSOIL Oil Filter ASF-25 | 13/16-16 Spin-On

AMSOIL Oil Filter ASF-25 — 13/16-16 Spin-On

Overview

The AMSOIL ASF-25 is a legacy full-flow spin-on engine oil filter in the short GM filter family, using the common 13/16"-16 mounting thread. It removes abrasive contaminants from circulating engine oil while maintaining the flow required to protect bearings, journals, and other lubricated components. ASF-25 is the older AMSOIL number for the filter now catalogued as EaO25, and it cross-references to WIX 51069, Sierra 18-7824, and several well-known MerCruiser and Volvo Penta numbers. Always confirm the existing filter number, thread, and gasket dimensions against your engine before ordering.

Compatible Applications

• GM-based MerCruiser sterndrive and inboard gasoline engines (see cross-reference numbers below)
• Volvo Penta GM-based gasoline inboard and sterndrive engines
• OMC sterndrive and inboard gasoline engines
• Crusader and Pleasurecraft Marine (PCM) GM-based engines
• Chris-Craft and Marine Power GM-based inboard applications
• Compatible older GM gasoline automotive and industrial engines with 13/16"-16 filter thread
• Confirm engine model, serial number, filter location, and existing filter number before ordering — many GM-family engines use different filter formats depending on year, marinizer, and filter-head configuration

Important — V6 marine engines: Several MerCruiser V6 engines use a filter mounted directly on the engine block rather than on a remote filter head. These applications may require a different filter. Confirm the existing filter number for V6 installations before ordering.

Dimensions

• Thread: 13/16"-16
• Height: approx. 3.82 in. / 97 mm
• Outside diameter: approx. 3.66 in. / 93 mm
• Nominal filtration: 21 microns
• Flow capacity: approx. 9–11 GPM

Cross-Reference / Alternate Part Numbers

The following numbers are associated with the ASF-25 / EaO25 filter family:

• AMSOIL: ASF-25, ASF25, EaO25
• WIX: 51069, 51046
• NAPA Gold: 1069, 1046
• Baldwin: B27
• Donaldson: P550025
• Fleetguard: LF651
• FRAM: PH30
• ACDelco: PF25
• Sierra: 18-7824
• MerCruiser: 32716, 32717, 35-802885Q, 54111, 866340Q02
• Volvo Penta: 835440, 835440-9, 3850559
• OMC: 173232, 502901, 502902
• Crusader: 201104
• Pleasurecraft / PCM: R077002

Cross-reference numbers are provided as a fitment aid only. Always confirm the original filter number and full engine application before substituting.

Service Interval

Replace the oil filter at every engine oil change, or at the interval specified by the engine manufacturer. Replace sooner if:

• Fuel, coolant, water, or debris contamination is found in the oil
• The engine has operated at extended low-speed (trolling) or high-load conditions
• The engine has been in seasonal storage
• Internal engine repairs have been performed
• Abnormal oil pressure conditions have been observed

Old-stock note: Do not install an ASF-25 filter if the canister is rusted or dented, the gasket is hardened or cracked, or the storage history is uncertain.

Installation Notes

• Remove the old filter and confirm its gasket has not remained on the filter head — a double-gasket condition will cause an immediate oil leak
• Clean the mounting surface on the filter head
• Compare the new filter’s thread size, gasket diameter, and body length with the removed filter
• Lightly coat the new filter’s gasket with clean engine oil before installation
• Install by hand until the gasket seats, then tighten per the filter manufacturer’s specification — do not overtighten
• Refill the engine with the specified oil grade and quantity
• Start the engine and confirm normal oil pressure immediately
• Inspect the filter body and gasket for leaks during the first few minutes of operation
• Shut down, allow oil to settle, recheck and correct the oil level

Related Products

• Sierra Marine Short GM Oil Filter 18-7824-2 (same filter family, Sierra-branded)
• Mercury MerCruiser Quicksilver Oil Filter 822626Q15
• Crusader / PCM Oil Filter with Gasket R077001
• AMSOIL 15W-40 Heavy-Duty Diesel & Marine Oil AME1GC — 3.78 L
• Mercury Quicksilver Oil Filter Adaptor O-Ring 25-33756
• Mercury MerCruiser 16779 Remote Oil Filter Adaptor Gasket — 4.3L V6
• Volvo Penta OEM Marine Engine Oil 21681794
• Browse All Oil Filters

Technical FAQ

Is ASF-25 still in production?

ASF-25 is a legacy AMSOIL part number. The current AMSOIL catalog equivalent is EaO25. If you are ordering a replacement and only have the ASF-25 number, cross-reference to EaO25 or WIX 51069 to confirm the correct current part.

How do I confirm this filter fits my engine?

The safest method is to check the part number on the existing filter or in your engine’s service manual. The 13/16"-16 thread is common to many GM-based engines, but filter height, gasket diameter, and valve configuration can differ. Confirming the existing OEM filter number (MerCruiser, Volvo Penta, OMC, etc.) against the cross-reference list above is more reliable than matching by thread alone.

Can I use ASF-25 on my MerCruiser V6 4.3L?

The 4.3L V6 MerCruiser uses different filter configurations depending on year and whether the filter is remote-mounted or block-mounted. Check the filter number currently on your engine — if it matches one of the MerCruiser cross-references listed above (32716, 32717, 35-802885Q, 866340Q02), ASF-25 / EaO25 is in the correct family. If your V6 uses a different filter number, do not assume fitment from the V8 cross-reference.

What is the difference between ASF-25 and EaO25?

They are the same filter family — ASF-25 is the older AMSOIL part number; EaO25 is the current designation. The physical filter and specifications are equivalent. If you have a stock of ASF-25 filters, they are the correct product for the same applications.

Can I use Sierra 18-7824 instead?

Yes — the Sierra 18-7824 is in the same filter family and is a widely used marine equivalent. Confirm the existing filter dimensions as above before substituting any brand.

Parts Desk Insights

Best use case: The ASF-25 is the right filter for customers maintaining older GM-based marine gasoline engines — MerCruiser 350 / 454 inboards and sterndrives, Volvo Penta 5.0 and 5.7L GL/GS, OMC inboards, and Crusader / PCM applications where this short GM filter format is specified. At $17.64 it is an accessible, quality option for customers who know their existing filter number and just need a reliable stocking cross-reference. The legacy ASF-25 number comes up frequently with older AMSOIL stockists and customers carrying over historical service records.

Common customer questions: The most frequent issue is customers using the 13/16"-16 thread to justify fitment without checking body length or gasket diameter — particularly on V6 MerCruiser applications where the filter may be block-mounted rather than remote-mounted. Always ask for the existing filter number if the customer is unsure. The second common question is whether ASF-25 and EaO25 are the same thing — they are, but customers with historical records or older AMSOIL invoices often have only the ASF-25 number.