How to distinguish between engine oil and gear oil?

[OJade]

Engine oil and gear oil operate in different working environments. Gear oil is primarily used in manual transmissions, reducers, and differentials, while engine oil is mainly used in automobile engines. Since gear teeth engage through direct contact, gear oil requires extremely high viscosity specifications, whereas engine oil has relatively lower viscosity requirements. Relevant information about engine oil is as follows: 1. Introduction: Engine oil, also known as engine lubricant (English name: Engine-oil), has a density of approximately 0.91×10³ (kg/m³). It serves multiple functions such as lubrication and friction reduction, auxiliary cooling, sealing and leakage prevention, rust and corrosion protection, as well as shock absorption. It is often referred to as the "blood" of a car. 2. Composition: Engine oil consists of two main components: base oil and additives. Base oil is the primary constituent of lubricating oil, determining its fundamental properties, while additives compensate for and enhance the shortcomings of the base oil, providing additional performance characteristics. Additives are an essential part of lubricating oil.

[LaCarter]

A couple of days ago, my neighbor asked me how to distinguish between engine oil and gear oil. Having driven trucks for over a decade, I do have some experience with this. Mainly, check the packaging labels: engine oil bottles will display viscosity grades like 5W-30, while gear oil is usually labeled with gear oil grades such as GL-4/GL-5. You can also smell them—gear oil has a pungent sulfur-like odor, whereas engine oil has a milder scent. There’s a color difference too: fresh engine oil is golden yellow, while gear oil tends to be a darker green. Last time during maintenance, I watched the mechanic perform a viscosity test—gear oil barely moved when dripped on a metal plate, while engine oil flowed much faster. The most crucial point is not to mix them up: putting gear oil in an engine will definitely cause problems, and using engine oil in a transmission will lead to gear grinding. I recommend storing them separately and labeling the bottles clearly with a marker pen for their intended use.

[BrielleDella]

Over the years working in the auto repair shop, I've relied on three main methods to distinguish these two types of oil. First, check the product standards - engine oil bottles bear API certification marks like SP/SN, while gear oil is labeled with transmission-specific specifications such as SAE 75W-90. Second, observe the viscosity - at room temperature, gear oil pours out thick like syrup, whereas engine oil is much thinner and feels slicker when poured on hands. Third, examine the fresh oil's appearance - unsealed gear oil shows bluish-green reflections on its surface, while engine oil appears as amber-colored transparent liquid. I remember once when an apprentice mistakenly added gear oil into an engine, the oil pump couldn't draw it properly, resulting in bearing shell corrosion that cost over 8,000 RMB to repair. Now I always advise car owners to keep the original packaging and avoid using empty containers for storing waste oil indiscriminately.