80W-90 Gear Oil: When to Use It (and When Not To)
By Travis Knappett, Kompo® Oil & Grease Specialist at HTS Spares.
Choosing the right oil for your vehicle or machinery isn’t just a detail - it’s a critical maintenance decision. One common question we get at HTS Spares is:
Can I use 80W-90 gear oil in my engine or hydraulic system?
The answer is definitely not. Unless your manufacturer explicitly approves it. Let’s break down why.
What Makes 80W-90 Gear Oil Special?
80W-90 isn’t just another oil, it’s a heavy-duty gear lubricant. Here’s what sets it apart:
- Extreme Pressure (EP) Additives - Protect gears and axles under heavy load
- Viscosity - Thick enough to maintain a protective film in high-pressure gear systems
- Target Applications - Manual gearboxes, differentials, and axles
Unlike engine or hydraulic oils, 80W-90 is designed for metal-on-metal gear contact, not high-speed pumps or pistons.
Why You Shouldn’t Swap It for Engine or Hydraulic Oil
Using gear oil in engines or hydraulics may cause:
- Poor Flow & Lubrication - Gear oil is too thick for engine circulation
- Increased Drag & Friction - EP additives are great for gears but hinder efficiency in hydraulic pumps
- Seal Wear & Leaks - Hydraulic and engine seals can be damaged by the wrong viscosity
Bottom line: matching oil to its system isn’t just recommended - it’s essential.
Where 80W-90 Shines
When used correctly, 80W-90 provides exceptional protection for:
- Differentials - Keeps gears smooth under heavy load
- Axles - Reduces wear in high-torque conditions
- Manual Gearboxes - Ensures quiet, efficient operation
At HTS Spares, our KOMPO® range of gear oils is engineered to deliver:
- Maximum wear protection for extreme conditions
- Long-lasting performance in both high and low temperatures
- Reliable operation for vehicles and industrial machinery
Choosing the Right Lubricant for Every System
Not all oils are created equal. Here’s a quick guide:
| System | Recommended Lubricant | HTS Spares KOMPO® Option |
|---|---|---|
| Engine | Engine oil | KOMPO® Engine Oils |
| Hydraulic | Hydraulic oil | KOMPO® Hydraulic Oils |
| Gearbox / Axle | 80W-90 gear oil | KOMPO® Gear Oils |
| Bearings / Joints | Grease | KOMPO® High-Performance Greases |
Using the right product ensures maximum efficiency, reliability, and lifespan. Even the best gear oil, like KOMPO® 80W-90, can’t substitute for engine or hydraulic oil.
Quick Tips from HTS Spares
- Always check the OEM manual before swapping oils
- Use KOMPO® gear oils and greases for heavy-duty protection
- Don’t mix oil types unless explicitly recommended
Correct lubrication may seem simple, but it’s the difference between smooth operation and expensive repairs.
For more advice, or to source high-quality oils and lubricants, please contact me, I would be pleased to help - travis.knappett@htsspares.com / 01432 373350.
