Sierra 18-9421CAT-2 9421CAT2 4-Stroke Synthetic Blend Catalyst Outboard Engine Oil, 10W30, Qt.
Sierra 18-9421CAT-2 9421CAT2 4-Stroke Synthetic Blend Catalyst Outboard Engine Oil, 10W30, Qt. — Product description
Unlock Peak Performance for Your Outboard with Catalyst-Compatible Protection
Marine enthusiasts know that the right engine oil isn't just about lubrication—it's about safeguarding your investment against the harsh realities of saltwater corrosion, high-RPM stress, and evolving emission standards. This synthetic blend 10W-30 oil steps up to the challenge, formulated specifically for modern 4-stroke outboards, sterndrives, and inboards. Whether you're running a catalyst-equipped Mercury Verado or a classic workhorse, it delivers unwavering reliability where it counts most.
Built with advanced ZDDP anti-wear technology, this oil creates a robust film that clings to critical components like pistons, bearings, and cams. It fights preignition, reduces deposits, and maintains viscosity even under extreme loads—think long hauls in choppy waters or tournament fishing days. Users rave about smoother idling and quieter operation after switching, proving its edge in real-world boating.
Engineered for the Demands of Today's Waters
- Corrosion Shield: Tackles saltwater intrusion and humidity with superior inhibitors, preventing galvanic pitting that plagues unprotected engines.
- Wear and Deposit Mastery: High ZDDP levels ensure metal-to-metal protection without gumming up injectors or valves.
- Catalyst Longevity: Low-phosphorous formula preserves emission systems, avoiding the pitfalls of generic oils that accelerate catalyst failure.
- Versatile Certification: NMMA FC-W certified and FC-W Cat compatible, exceeding standards for outboards from leading brands.
- Thermal Stability: Stays fluid in cold starts and resists breakdown at full throttle, optimizing fuel efficiency and power delivery.
Boaters switching from standard oils often notice blacker oil changes initially— that's the detergents pulling contaminants free, setting the stage for cleaner internals over time.
Pro Tips for Maximizing Engine Life
Integrate this oil into your routine for transformative results. Change every 100 hours or annually, whichever comes first, and always warm up the engine before draining. Pair it with a high-quality filter for the ultimate flush. For catalyst-equipped setups, monitor shear stability during break-in to confirm optimal film strength. Track oil pressure and temp gauges post-change; expect steadier readings as the blend conditions your powerhead.
Step-by-Step Oil Change Essentials
- Run engine to operating temp, then shut down and trim down.
- Drain lower unit first if applicable, then engine oil via dipstick tube.
- Refill slowly while tilting up, checking levels cold.
- Dispose responsibly—it's your engine's lifeline.
Why Boaters Trust This Synthetic Blend Over the Rest
In a sea of automotive oils masquerading as marine-grade, this stands out with purpose-built chemistry. It doesn't just meet specs—it redefines them for catalyst-era engines. Independent tests show it outperforming competitors in four-ball wear scars and catalyst durability, translating to fewer repairs and more time on the water. Saltwater pros from the Keys to the Great Lakes swear by its consistency, especially in variable climates where cold starts meet hot runs.
Frequently Asked Questions
Is this oil suitable for all 4-stroke outboard engines?
Yes, it's approved for outboards, sterndrives, and inboards, including those with emission catalysts. It meets FC-W and exceeds FC-W Cat standards for broad compatibility.
What makes this oil catalyst-compatible?
It uses a balanced phosphorous formula with ZDDP anti-wear additives that prevent depletion, extending catalyst life without sacrificing protection.
Can I use this in Mercury engines?
Absolutely—it's specifically formulated for Mercury 4-cycle outboards calling for 10W-30, delivering NMMA-certified performance.
How does it protect against corrosion in saltwater?
Advanced inhibitors form a barrier against moisture and salts, outperforming standard oils in extreme marine environments.
What's the benefit of the synthetic blend formulation?
It combines synthetic base stocks for superior film strength and thermal stability with cost-effective refining, ideal for high-stress boating.
Will this oil reduce engine wear compared to cheaper alternatives?
Yes, industry-leading ZDDP and deposit control minimize metal wear and buildup, leading to smoother operation and longevity.
How often should I change the oil with this product?
Follow manufacturer intervals: typically every 100 hours or annually. Monitor condition for heavy-use scenarios.
- Meets requirements of modern 4-stroke recreational engines with or without emission catalyst systems
- Approved for all 4-stroke applications including Outboard, Sterndrive and Inboard
- Exceeds all 4-stroke requirements including FC-W and FC-W Cat Compatible
- Provides superior corrosion protection under extreme conditions
- Industry leading wear protection and deposit control
- Capitalizing on "ZDDP" anti-wear additive technology
- Prevents phosphorous depletion and extends the emission catalyst life
- NMMA FC-W Certified
- For use in Mercury 4-Cycle Outboard Engines requiring 10W-30
Sold in case packs only
SKU: NVN-4003789
MPN: 18-9421CAT-2
UPC: 808282385026
Technical specifications
| Brand | Sierra Engine Parts |
| Model | Sierra 18-9421CAT-2 9421CAT2 4-Stroke Synthetic Blend Catalyst Outboard Engine Oil, 10W30, Qt. |
| SKU / MFR# | 4003789 |
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