AMSOIL 75W-90 Long Life Synthetic Gear Lube – 1 Qt (FGRQTC)
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AMSOIL 75W-90 Long Life Synthetic Gear Lube – 1 Qt (FGRQTC)
| Part Number / SKU | FGRQTC |
| Brand | AMSOIL |
| Product Family | Long Life 100% Synthetic Gear Lube (FGR) |
| Official Product Type | Full Synthetic Gear Lubricant |
| Viscosity Grade | 75W-90 |
| Container Size | 1 US Quart (~946 mL) |
| Weight | ~0.95 kg |
| Extended Drain Rating | Up to 500,000 miles / 805,000 km where approved by equipment manufacturer |
What This Product Is
AMSOIL FGRQTC is the Canadian quart (1 qt) package of the AMSOIL Long Life 100% Synthetic Gear Lube in 75W-90 viscosity. It is a full synthetic gear oil engineered for axle, differential, and gearbox applications in on-road and off-road equipment where the manufacturer specifies a 75W-90 synthetic gear lubricant. The full synthetic formulation provides high-load gear and bearing protection, shear stability, cold-weather fluidity, and extended drain capability where the equipment manufacturer permits.
Compatible Applications
- Rear axle differentials and front axles requiring 75W-90 synthetic gear lube
- Manual gearboxes and transfer cases specifying 75W-90 GL-4 or GL-5 gear oil
- Heavy-duty over-the-road trucks and commercial vehicles
- Light-, medium-, and heavy-duty pickup trucks and SUVs
- Motorhomes and recreational vehicles
- Off-road equipment, buses, delivery vehicles, and utility vehicles
- Tractors and agricultural equipment specifying 75W-90 synthetic gear lube
- Emergency vehicles requiring extended-drain synthetic drivetrain lubricants
Always confirm the required viscosity grade, API/GL service specification, and any limited-slip friction modifier requirement in the vehicle or equipment service manual before use. Do not select by viscosity grade alone.
Package Size Options (FGR Family)
- FGRQTC — 1 quart (this item)
- FGR1G / FGR1G-EA — 1 gallon jug
- FGR05 — 5 gallon pail
- FGR16 — 16 gallon keg
- FGR55 — 55 gallon drum
- FGR27 — 275 gallon tote
Contact us for availability on larger package sizes.
Related Products
Fitment & Selection Notice
Confirm the following before use:
- Required viscosity grade is 75W-90
- Required API/GL specification (GL-4, GL-5, MT-1, or other) matches the product’s listed approvals — confirm on the AMSOIL product data sheet
- Limited-slip differential requirement: if the axle uses a limited-slip clutch pack, confirm whether a separate friction modifier is required or whether an LS-approved gear lube is specified
- Equipment manufacturer’s drain interval approval for extended-drain use
- Marine gearbox and sterndrive applications: some marine drives specify proprietary fluids — confirm the drive manufacturer’s approved lubricant list before use
When to Replace
- At or before the equipment manufacturer’s specified drain interval
- Oil appears milky or watery (water intrusion)
- Oil smells burnt or contains visible metal particles on the drain plug magnet
- Differential or gearbox becomes noisy, overheats, or leaks
- Unit has been opened for repair or seal replacement
- Contamination from cross-filling with incorrect lubricant
Service Notes
- Drain and refill according to the equipment manufacturer’s procedure
- Clean fill and drain plug areas before opening
- Inspect the drain plug magnet for metal debris and note any unusual accumulation
- Replace sealing washers or copper crush washers where specified
- Fill only to the manufacturer’s specified level — overfilling can cause seal damage and leaks
- For limited-slip differentials, confirm friction modifier requirements before filling
Technical FAQ
What does 75W-90 mean?
75W-90 is a multi-grade gear oil viscosity designation. The 75W indicates the oil’s cold-flow rating (the lower the number, the better the cold-weather fluidity); the 90 is the high-temperature viscosity grade. A 75W-90 synthetic flows well in cold conditions while providing a 90-weight film at operating temperature.
Can I use this in a limited-slip differential?
Confirm the specific axle’s requirement. Some limited-slip differentials require a gear oil with a built-in friction modifier or a separately added friction modifier to prevent clutch-pack chatter. Check the vehicle or axle manufacturer’s specification and the AMSOIL FGR product data sheet for LS compatibility before use.
Is this suitable for marine gearboxes or sterndrives?
Some marine transmissions and sterndrives accept 75W-90 gear lube; others specify proprietary fluids such as Volvo Penta QL, Mercruiser High-Performance Gear Lube, or similar. Always confirm the specific drive or transmission manufacturer’s approved lubricant specification before use in a marine drivetrain application.
What is the extended drain interval?
AMSOIL rates the FGR family for up to 500,000 miles / 805,000 km in over-the-road trucking applications where the equipment manufacturer approves extended-drain use. For other equipment types, follow the manufacturer’s service interval unless the extended-drain capability has been specifically approved for that application.
Parts Desk Insights
The safe match for gear lube is viscosity grade plus the required API/GL specification — 75W-90 gets you part of the way, but confirming GL-4 vs. GL-5 and any limited-slip requirement is the step that avoids noise, chatter, or premature wear. The most common issue in this product category is customers selecting by viscosity alone without checking the LS friction modifier requirement. For marine applications specifically, it’s worth confirming against the drive or transmission manufacturer’s approved lubricant list — Volvo Penta and Mercruiser both publish specific approvals for their sterndrives and transmissions that may or may not align with a generic 75W-90 synthetic.
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.