The Difference Between Engine Oil and Transmission Fluid
2 Answers
The difference between engine oil and transmission fluid lies in their viscosity and lubricity. Under normal driving conditions, the temperature of transmission fluid is typically below 135°C, while engine oil generally operates below 50°C. Below are the functions of engine oil and transmission fluid: 1. Engine Oil: Also known as engine lubricant (English name: Engine-oil), with a density of approximately 0.91×10³ (kg/m³), it serves to lubricate and reduce friction in the engine, assist in cooling, seal against leaks, prevent rust and corrosion, and provide shock absorption. It is often referred to as the 'blood' of a car. Engine oil consists of base oil and additives. The base oil is the primary component of lubricating oil, determining its fundamental properties, while additives compensate for and enhance the performance shortcomings of the base oil, imparting new characteristics, making them an essential part of lubricating oil. 2. Transmission Fluid: This is a lubricant used to keep the gear system clean, ensuring the proper functioning of the transmission and extending the lifespan of the transmission components.
As an experienced car owner, I used to be confused about the difference between engine oil and transmission fluid when doing DIY maintenance, but now I understand much better. Engine oil is specifically for lubricating the engine—it reduces friction, cleans impurities, and helps cool internal components. Its viscosity varies significantly; thinner oils like 5W-30 are used in winter, while thicker ones are preferred in summer. It requires frequent changes, typically every 5,000 to 10,000 kilometers, otherwise the engine may overheat and smoke. Transmission fluid, on the other hand, is designed for automatic or manual transmissions, ensuring smooth gear shifts and protecting gears. Its viscosity is more stable, and it doesn’t need changing as often—only around every 50,000 kilometers. I once saw a friend mistakenly add engine oil to the transmission, which caused it to seize up and cost thousands to repair. So, regularly checking the vehicle manual is crucial—don’t cut corners by using the wrong fluids. It’s best to have a technician check fluid conditions during maintenance. In summer heat, transmission fluid degrades more easily, so that’s something to watch out for.
