Sierra Synthetic Blend 10W30 FC-W 4-Stroke Outboard Engine Oil, 1 Qt. – 9421CAT2
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Sierra Synthetic Blend 10W30 FC-W 4-Stroke Outboard Engine Oil – 1 Qt. | Part #9421CAT2
The same NMMA FC-W and FC-W Cat Compatible certified synthetic-blend 10W30 formulation as the gallon, in a single-quart bottle. Designed for 4-stroke outboard engines — including Mercury 4-cycle outboards specifying 10W30 — and approved for outboard, sterndrive, and inboard applications with or without emission catalyst systems. Sold in case packs only.
Key Features
- NMMA FC-W® Certified & FC-W Cat Compatible — approved for 4-stroke outboard, sterndrive, and inboard engines with and without emission catalyst systems
- Approved for Mercury 4-cycle outboards requiring 10W30 — a direct fit for Mercury and Mariner 4-stroke outboard applications
- Catalyst-safe ZDDP technology — prevents phosphorus depletion and extends emission catalyst life
- Synthetic blend base — better thermal stability and oxidation resistance than conventional mineral oil
- SAE 10W30 multi-grade — good cold-start flow with adequate high-temperature viscosity for outboard use
- Superior corrosion protection — guards internal engine components against moisture and salt exposure
- Industry-leading wear protection and deposit control — keeps engine internals clean across the full service interval
Specifications
- Viscosity: SAE 10W30
- Certification: NMMA FC-W®, FC-W Cat Compatible
- Application: 4-stroke outboard, sterndrive, and inboard marine engines; specifically approved for Mercury 4-cycle outboards requiring 10W30
- Size: 1 US quart (946 mL)
- Part number: 9421CAT2
- Sold as: Case packs only
Parts Desk Insights
Best use case: The quart bottle is the most practical format for a top-up between oil changes, keeping a spare quart aboard, or for smaller 4-stroke outboards with lower oil capacities where a full gallon would leave significant leftover product. It’s also a good stocking unit for service shops that want a ready-to-use quantity for single top-up jobs. For a complete single-engine oil change on a mid-size or larger 4-stroke outboard, the Sierra Synthetic Blend 10W30 FC-W 4-Stroke Outboard Engine Oil, 1 Gallon – 9421CAT3 is the more economical choice per litre. For high-volume shop use, the Sierra 10W30 FC-W 4-Stroke Outboard Oil, 55-Gallon Drum – 94207 is available. If your engine calls for a non-catalyst-specific 10W30 FC-W oil, see the Sierra 10W30 FC-W 4-Stroke Outboard Oil, Qt. – 94202. For the OEM Mercury 10W30 option, see Mercury Synthetic Blend Engine Oil 10W30 – 8M0149203.
Compatibility note: Always confirm your engine manufacturer’s oil specification — viscosity grade, FC-W certification level, and any OEM approvals — before ordering. Sold in case packs; confirm case quantity at time of order.
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.