Synthetic 75W90 Gear Oil – Marine Lower Unit & Transmission Oil
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You have 30 days to request a return. All sale items are final sale.
Synthetic 75W90 Marine Gear Oil
A full-synthetic, GL-5 rated gear oil engineered for the unique demands of marine drivetrains. Whether you're servicing an outboard lower unit, a stern drive gear case, or a marine transmission, this 75W90 formula delivers reliable protection against wear, corrosion, and water contamination — season after season.
Specifications
- Viscosity Grade: 75W90
- Type: Full Synthetic
- API Service: GL-5
- Volume: 1 Qt
Compatible Applications
- Outboard motor lower units
- Stern drive (I/O) gear cases
- Inboard marine transmissions
- V-drives and jet drives
Key Features
- Extreme-pressure (EP) additives protect gears and bearings under heavy load
- Excellent water separation — resists emulsification in saltwater and freshwater environments
- Enhanced thermal stability maintains viscosity at high operating temperatures
- Anti-corrosion inhibitors protect metal surfaces during storage and off-season layup
- Compatible with most OEM synthetic gear lubricants
Parts Desk Insights
Best use case: Routine lower unit and gear case service on outboards and stern drives — especially where the OEM spec calls for a GL-5 75W90 synthetic. This is a solid value-tier choice for annual gear oil changes or post-season layup service. For brand-specific OEM lubricants, see the Volvo Penta Transmission Oil 1141680 or Volvo Penta 80W-90 GL-5 Gear Lube (1141676).
When changing gear oil, pair this with a Lower Unit Gear Oil Pump with Adapter for a clean, no-spill fill. For a complete kit including lube and pump, consider the Sierra Hi-Performance Gear Lube & Pump Kit.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 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.