Gear Lube Hi-Performance Synthetic Blend 10oz | Sierra 18-9650-0

Sierra 18-9650-0 Hi-Performance Synthetic Blend Gear Lube | 10 oz. | 80W-90 GL-5 | Outboard & Sterndrive | Replaces Mercury, OMC, Yamaha

The Sierra #18-9650-0 is a 10 oz. tube bottle of hi-performance synthetic blend gear lube for outboard and sterndrive (I/O) lower units. 80W-90 viscosity, GL-5 rated. Blue-green color. Formulated to protect gears, bearings, and internal gearcase components under high-load operating conditions, and engineered to meet or exceed the performance of OEM hi-performance lubricants. Replaces Mercury Quicksilver Hi-Performance Blend, OMC Ultra-HPF Blend, and Yamaha Yamalube LUB-GEARL-11-00.

Product Details:

• Part Number: 18-9650-0 (Sierra)
• SKU: SIERRA-18-9650-0
• Manufacturer: Sierra
• Type: Hi-Performance Synthetic Blend Gear Lube
• Size: 10 oz. tube bottle
• Viscosity: 80W-90
• Rating: GL-5
• Color: Blue-green
• Application: Outboard and sterndrive (I/O) lower unit gearcases
• Optional Pump: Sierra 18-9781 gear lube pump (sold separately)

Cross-Reference — Replaces:

• Mercury Quicksilver: Hi-Performance Blend lubricant
• OMC: Ultra-HPF Blend lubricant
• Yamaha: Yamalube LUB-GEARL-11-00

Additional Information

80W-90 GL-5 — High-Load Marine Gearcase Specification:

The 18-9650-0 is an 80W-90 viscosity GL-5 rated lubricant. GL-5 is the API service classification for hypoid gear lubricants operating under high shock loads — the classification required for marine lower unit gearcases, which use hypoid or spiral bevel gear sets that operate under high pressure and sliding contact between gear teeth. The 80W-90 viscosity provides the film thickness required for outboard and sterndrive gearcase operating temperatures and clearances. Using a lower GL rating (GL-4 or below) or incorrect viscosity risks inadequate gear film strength and accelerated gear wear under marine operating loads.

Synthetic Blend — Hi-Performance vs. Standard Gear Lube:

The 18-9650-0 is a synthetic blend formulation — a combination of conventional base oil and synthetic base oil — designed to exceed the protection level of conventional mineral-base gear lubes. Many high-output outboard and sterndrive manufacturers specify a hi-performance or premium gear lube for engines operating under sustained high-RPM or high-load conditions. The synthetic blend formulation provides:

• Higher film strength under shock and sustained high loads compared to mineral-base 80W-90
• Better thermal stability at elevated gearcase temperatures in high-RPM applications
• Improved water resistance — marine gearcases are exposed to water through prop shaft seals during normal operation
• Shear stability — synthetic blend base oils maintain viscosity under the high mechanical shear in marine hypoid gear sets better than conventional oils

Blue-Green Color — Lube Identification:

The blue-green color of the 18-9650-0 is a visual identification marker that distinguishes hi-performance synthetic blend gear lube from standard mineral-base gear lube (typically yellow or clear) and from full-synthetic formulations. When draining the gearcase at service, note the color of the old lube — if the drained lube is milky, cream-colored, or gray rather than blue-green, water has entered the gearcase through a failed prop shaft or input shaft seal and the seals should be replaced before refilling.

OEM Replacement — Mercury, OMC, Yamaha:

The 18-9650-0 replaces the hi-performance blend lubricants specified by three major OEM brands:

• Mercury Quicksilver Hi-Performance Gear Lube — the OEM specification for Mercury and MerCruiser hi-performance applications
• OMC Ultra-HPF Blend — the OEM hi-performance specification for Johnson and Evinrude outboards and OMC sterndrives
• Yamaha Yamalube LUB-GEARL-11-00 — the Yamaha hi-performance gear lube specification

Confirm your engine manufacturer's gear lube specification (standard vs. hi-performance) in the service manual before ordering to ensure the 18-9650-0 is the correct formulation for your application.

10 oz. Tube Bottle — Gear Lube Pump Recommended:

The 18-9650-0 is packaged in a 10 oz. squeeze tube bottle. For cleaner, more controlled gearcase filling, the Sierra 18-9779 universal gear lube pump (sold separately) threads directly into the gearcase fill port and draws from the bottle, eliminating spills and ensuring complete fill. A pump is particularly useful when filling sterndrives where the fill port is oriented vertically and squeeze-bottle filling is awkward.

Service Interval — Annual or Per Manufacturer Specification:

Change gearcase gear lube annually or per your engine manufacturer's service interval, whichever comes first. Always inspect the drained lube for water contamination (milky or gray color) and metal particles before refilling. Water-contaminated lube or metal particles in the drained lube indicate internal gearcase problems that should be addressed before returning to service.

Installation Notes:

• Confirm your engine's gear lube specification (hi-performance vs. standard) in the service manual before ordering
• Drain gearcase fully and inspect drained lube for water (milky color) or metal particles before refilling
• Fill from the lower fill port upward until lube flows from the vent port — install vent screw first, then fill screw
• Use Sierra 18-9779 gear lube pump (sold separately) for cleaner, controlled filling
• Do not mix hi-performance synthetic blend with mineral-base standard gear lube if possible — complete drain and refill is preferred at each service

Frequently Asked Questions

1. Is this the correct gear lube for my outboard?
Confirm your engine manufacturer's gear lube specification in the service manual — some engines specify hi-performance gear lube, others specify standard. The 18-9650-0 replaces Mercury Quicksilver Hi-Performance Blend, OMC Ultra-HPF Blend, and Yamaha Yamalube LUB-GEARL-11-00. If your engine specifies one of these OEM lubes, the 18-9650-0 is the correct Sierra replacement.

2. What does GL-5 mean?
GL-5 is the API classification for extreme-pressure (EP) hypoid gear lubricants rated for high shock-load applications. Marine outboard and sterndrive gearcases require GL-5 rated lubricant due to the high contact pressures in the gear set. Using a GL-4 or lower rated lubricant in a GL-5 application risks inadequate film strength and gear damage.

3. What does the blue-green color mean?
Blue-green is the color of Sierra's hi-performance synthetic blend gear lube — it distinguishes this formulation from standard mineral-base gear lube. If drained lube is milky or gray instead of blue-green, the gearcase has water intrusion through a failed seal and should be repaired before refilling.

4. Can I use this in my sterndrive as well as my outboard?
Yes — the 18-9650-0 is formulated for both outboard and sterndrive (I/O) lower unit gearcases. Confirm your sterndrive manufacturer's gear lube specification in the service manual.

5. Do I need a pump to use this?
A pump is not required but is strongly recommended for cleaner, more controlled filling. The Sierra 18-9779 universal gear lube pump (sold separately) threads into the gearcase fill port and draws from the bottle. See our Sierra 18-9779 listing for details.