Gear Oil
Gear oils are specialised lubricants designed for gearboxes, differentials, and axles. They are classified by API GL ratings (GL-4 for manual transmissions, GL-5 for hypoid gears) and SAE viscosity grades. GL-5 oils contain extreme-pressure additives for heavy-duty applications, while GL-4 oils are formulated for lighter loads and brass synchroniser compatibility. Limited-slip gear oils include friction modifiers to prevent differential chatter.
Key Specifications
Brands Offering Gear Oil Products
Frequently Asked Questions
What is the difference between GL-4 and GL-5 gear oil?
GL-4 gear oils are designed for manual transmissions and moderate-duty gears, with lower levels of extreme-pressure (EP) additives that are compatible with brass synchronisers. GL-5 oils contain higher concentrations of sulphur-phosphorus EP additives for hypoid gears and heavy-duty differentials. Using GL-5 in a GL-4 application can damage brass components.
Do I need limited-slip gear oil for my differential?
If your vehicle has a limited-slip differential (LSD), you need a gear oil with friction modifiers specifically designed for LSDs, or you must add a separate friction modifier additive. Without the correct friction characteristics, you may experience differential chatter, noise during turns, and premature clutch wear.
Can I use synthetic gear oil instead of mineral?
Yes, synthetic gear oils generally offer superior performance including better low-temperature flow, improved thermal stability, and longer service life. They are particularly beneficial in extreme temperature conditions and heavy-duty applications. Ensure the synthetic oil meets the same API GL rating and SAE viscosity grade specified for your application.
Find Your Gear Oil Equivalent
Use the Universal Oil Matcher to instantly cross-reference gear oil products across Shell, Mobil, Castrol, Sinopec, Valvoline, Caltex, Fuchs, Penrite, and Gulf Western.
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