Gear oils are precision-engineered fluids built to safeguard gear trains in automobiles, heavy machinery, and industrial systems

Where engine oils focus on combustion byproducts, gear oils are built for shear resistance and load-bearing durability

Multiple gear oil variants exist, each tailored to unique mechanical environments and workload requirements

Understanding the differences between them helps ensure the right choice for your equipment, improving efficiency and extending component life

The SAE viscosity grading system is the industry standard for identifying gear oil flow characteristics

Common SAE grades include 75W-90, 80W-140, 85W-140, and straight-weight options like SAE 90 and SAE 140

The number before the w indicates the oil’s flow characteristics at low temperatures, while the number after indicates its thickness at operating temperature

A 75W-90 lubricant remains fluid during winter starts yet maintains protective film strength under operational heat

An improperly matched viscosity can result in accelerated wear, reduced fuel economy, or dangerous thermal runaway

Gear oils fall into two primary categories: conventional petroleum-based and advanced synthetic blends

Mineral-based oils are refined from crude oil and are generally more affordable

They perform reliably in everyday driving conditions and light industrial settings

Synthetic gear oils, however, are chemically engineered for superior performance

They offer better thermal stability, improved resistance to oxidation, and longer service life

Use synthetics when equipment faces constant overload, extreme temperatures, or prolonged operation without downtime

Gear lubricants are rated according to standardized performance tiers

API service categories—GL-1 to GL-6—indicate the level of extreme pressure protection

GL-1 suits low-load, low-speed applications like older manual gearboxes

GL-3 and GL-4 are for moderate to high-speed applications like passenger car transmissions

GL-5 is the most common for heavy-duty axles and differentials that require extreme pressure protection

GL-6 was developed for ultra-high-performance systems but has largely been phased out due to synchronizer wear concerns

Never assume—always verify the manufacturer’s specified API grade for your gear system

Some gear oils contain additives that serve specific purposes

EP additives form protective films that withstand crushing forces and prevent scoring

AW additives minimize pitting, scuffing, and micro-wear on gear teeth

These agents neutralize acidic byproducts and prevent oxidation-induced degradation

They’re critical in transmissions requiring precise synchronizer operation

Additive packages vary significantly between formulations and are not universally interchangeable

Certain LSD differentials demand اتوسرویس داوود specific friction characteristics—wrong oils trigger inconsistent engagement and noisy operation

Not all gear oils are interchangeable across vehicle systems

Automatic transmission fluids (ATF) and manual gear oils serve entirely different mechanical functions

Even within manual transmissions there are variations

Some older vehicles require gear oil while newer ones may need a specific synthetic fluid that meets manufacturer specifications

The manufacturer’s specifications are the only reliable source for fluid selection

Incorrect lubrication causes accelerated gear erosion, overheating, synchronizer damage, or complete gearbox seizure

The optimal gear oil balances temperature performance, load protection, and system compatibility

Taking the time to understand these differences ensures your gears run smoothly and last longer

If specifications are unclear, contact the OEM or a certified technician

Correct gear oil selection is fundamental to safe operation, regulatory compliance, and long-term asset value