What is the difference between automotive gear oil and engine oil?

[LaBradley]

The difference between automotive gear oil and engine oil lies in their working environments and primary focuses. Here is a relevant introduction about the differences between gear oil and engine oil: Different working environments: Gear oil is mainly used in manual transmissions, reducers, and differentials, while engine oil is primarily used in car engines. Since gear teeth engage through direct contact, gear oil must have extremely high viscosity specifications; otherwise, it cannot form an oil film at the gear engagement points. In contrast, engine lubrication involves mostly surface contact without the extreme high pressure generated during gear engagement, so its viscosity requirements are relatively lower. Different primary focuses: Gear oil emphasizes protecting gears under high temperatures, while engine oil focuses on its fluidity at low temperatures. Additionally, gear oil is strongly alkaline, whereas engine oil is weakly alkaline.

[EmersynFitz]

Back in my younger days driving old trucks, the difference between gear oil and engine oil was huge. Gear oil is specifically for transmissions and differentials where gears are pressed together, requiring thicker oil to withstand high pressure, like GL-5 grade with special additives to prevent gear wear. Change intervals are longer – manual transmission vehicles might go 50,000 km between changes. Engine oil circulates in the engine, lubricating pistons and bearings while also cooling and cleaning; it's thinner like 10W-40 and needs changing every 5,000 km. Never mix them – my buddy once used engine oil as gear oil and seized his transmission gears, costing thousands to repair. During regular maintenance, check oil levels and color – using the right oil extends vehicle life and saves big money.

[Bustamante]

From a principle perspective, automotive gear oil is designed for the transmission system. Gears in components like transmissions or rear axles need to withstand high impact pressures, so it has high viscosity and contains extreme pressure additives to protect metal surfaces. Engine oil is primarily used inside the engine to lubricate moving parts, clean carbon deposits, and cool the engine, with additives including antioxidants and cleaning formulations. Their API standards differ: gear oil has GL ratings (e.g., GL-4 for regular transmissions), while engine oil uses SAE viscosity grades like 5W-30. Misuse can cause failure—for example, using engine oil in a transmission may lead to oil film rupture and accelerated gear wear, while the reverse scenario could trigger engine overheating warnings. Always follow your vehicle manual to select genuine products and adopt a habit of checking every six months to prevent accidents.

[StTyler]

As a car enthusiast from the post-90s generation, I learned the differences when modifying to a manual transmission. Gear oil is specifically for transmissions, ensuring smooth shifting and wear resistance. It's thicker, like syrup, with longer change intervals, typically every 40,000-60,000 km. Engine oil keeps the engine running smoothly, with lower viscosity for better flow, requiring more frequent changes every 3 months or 5,000 km. Once, I mistakenly poured engine oil into the transmission, causing immediate loud noises and nearly causing serious damage. Later, I learned to change it myself, saving money and gaining skills. Remember, using the wrong type can lead to high risks of failure.