Gear Oil vs Engine Oil – Complete Difference Explained
Lubricants are the lifeblood of every vehicle. Whether it’s the powerful engine or the smooth transmission system, both depend on the right type of oil to perform efficiently. Yet, many vehicle owners still get confused between gear oil and engine oil — thinking they are the same.
In reality, they are completely different lubricants, each designed for a unique purpose. In this article, Bharat Lubricants, one of India’s trusted lubricant manufacturers, explains the key difference between gear oil and engine oil, their functions, and why using the correct one is crucial for vehicle health.
What Is Engine Oil?
Engine oil is specifically formulated to lubricate the moving parts inside your engine. It minimizes friction, reduces wear, keeps the engine clean, and cools the system.
Modern engine oils, such as Bharat MGEO 20W40, are blended with advanced additives that prevent sludge formation, improve mileage, and extend engine life.
Main Functions of Engine Oil:
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Lubricates pistons, crankshafts, and valves
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Reduces friction and overheating
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Cleans and prevents deposits or sludge
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Protects against rust and corrosion
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Enhances fuel efficiency and performance
What Is Gear Oil?
Gear oil is used to lubricate transmission systems, gearboxes, and differentials. Unlike engine oil, it is thicker and formulated to handle extreme pressure between metal surfaces inside gears.
Bharat Gear Oil EP 90 is one of the most trusted products for heavy-duty and commercial vehicles in India. It ensures smooth gear shifting, noise reduction, and long-lasting gearbox protection.
Main Functions of Gear Oil:
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Provides high-pressure (EP) protection between metal gears
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Reduces friction, wear, and heat in transmission systems
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Ensures smoother gear shifting
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Prevents rust and oxidation
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Extends gearbox life under heavy load and temperature
Gear Oil vs Engine Oil – Key Differences
| Feature | Engine Oil | Gear Oil |
|---|---|---|
| Purpose | Lubricates engine components | Lubricates gearbox & differential |
| Viscosity | Lower viscosity (thinner) | Higher viscosity (thicker) |
| Additives | Detergents, dispersants, anti-wear agents | Extreme Pressure (EP) and anti-foam additives |
| Temperature Range | Operates under combustion heat | Works under high-pressure gear friction |
| Smell | Less pungent | Strong sulfur or EP odor |
| Example | Bharat MGEO 20W40 | Bharat Gear Oil EP 90, EP 140 |
| Change Interval | 7,000 – 10,000 km (approx.) | 40,000 – 60,000 km (approx.) |
Understanding the Viscosity Difference
Viscosity refers to the oil’s thickness and ability to flow.
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Engine oils like SAE 20W40 are thinner to circulate easily at various engine temperatures.
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Gear oils like SAE 90 or 140 are thicker, forming a strong film between gear teeth to prevent wear.
Even though both may show numbers like “90” or “40,” they are based on different viscosity grading systems (engine oils follow SAE J300, while gear oils follow SAE J306). So, never confuse them!
Why You Should Never Use Engine Oil in Gearbox or Vice Versa
Many drivers assume oil is oil — but that’s a costly mistake!
Using the wrong lubricant can cause:
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Premature wear or damage to gears
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Excessive noise and vibration
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Poor performance and overheating
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Costly gearbox or engine repairs
Always use engine oil for engines and gear oil for transmissions — each is engineered for its specific role.
Bharat Lubricants – Powering India with the Right Oils
With over 40 years of experience, Bharat Lubricants offers a complete range of automotive and industrial lubricants made for Indian conditions.
Our Top Products Include:
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Bharat MGEO 20W40: For diesel and petrol engines, ensuring superior protection and mileage.
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Bharat Gear Oil EP 90 / EP 140: For gearboxes and differentials, offering unmatched load-carrying ability and smooth transmission.
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Bharat Differential Oil: For heavy-duty vehicles requiring long-lasting lubrication.
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Bharat Power Steering Oil: For effortless handling and steering performance.
Every product is manufactured under strict quality control and tested to meet global standards (API, SAE, and ISO certifications).
Which Oil Is Right for You?
| Vehicle Type | Recommended Engine Oil | Recommended Gear Oil |
|---|---|---|
| Cars/SUVs | Bharat MGEO 20W40 | Bharat Gear Oil EP 90 |
| Trucks/Buses | Bharat MGEO 15W40 | Bharat Gear Oil EP 140 |
| Tractors | Bharat MGEO 20W40 | Bharat Gear Oil EP 90 |
| Industrial Machines | Bharat Industrial Oil Series | Bharat Gear Oil EP 90/140 |
Maintenance Tip by Bharat Lubricants Experts
To maximize performance and lifespan of your vehicle:
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Always use manufacturer-recommended oil grades.
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Check oil levels regularly and top-up when necessary.
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Change oil filters during every oil change.
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Drain and refill gearbox oil every 40,000–60,000 km.
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Buy only from authorized Bharat Lubricants dealers to ensure quality.
Final Thoughts
The difference between gear oil and engine oil is not just in name — it’s in purpose, formulation, and performance.
Engine oil powers the heart of your vehicle, while gear oil keeps its movement smooth and efficient.
With Bharat Lubricants, you don’t have to worry about choosing the right one — our expert formulations guarantee power, protection, and performance for every vehicle type.