Sierra 25W-50 FC-W Synthetic Blend 4-Cycle Marine Engine Oil – 4 L
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Sierra 25W-50 FC-W Synthetic Blend Marine Engine Oil – 4 L
Engineered for the demands of the marine environment, this 25W-50 synthetic blend engine oil meets both NMMA FC-W and API SL certifications — the two benchmarks that matter most for 4-cycle outboard and inboard engines operating without a catalytic converter. The synthetic blend base provides a stable viscosity film across a wide temperature range, so your engine is protected whether you're idling in a hot marina or running hard offshore.
The formulation includes elevated levels of rust and corrosion inhibitors specifically chosen for salt and freshwater exposure, along with high-load additives that protect bearings and cylinder walls under sustained wide-open-throttle use.
- Viscosity: 25W-50
- Certification: NMMA FC-W / API SL
- Engine type: 4-cycle outboard and inboard (non-catalytic converter)
- Volume: 4 L
- Base: Synthetic blend
Parts Desk Insights
Best use case: Ideal for high-output 4-stroke outboard engines — particularly larger displacement motors (150 hp and up) running in saltwater or mixed conditions where corrosion protection and shear stability are priorities. Also well-suited for inboard gasoline engines in runabouts and cruisers that see regular seasonal use. If you run a smaller 4-stroke outboard or prefer a straight-weight option, see the Sierra 25W-50 FC-W Marine Engine Oil – 1 L for single-quart top-ups or mixed-fleet stocking.
Compatibility note: Confirm your engine OEM spec calls for FC-W rated oil. Not intended for 2-stroke engines or engines equipped with catalytic converters.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.