What is the difference between engine oil and transmission oil?

The best-known lubricants used in a car are engine oils and transmission oils. They are used in different places in the car and fulfil different functions.

Engine oils are used directly in the combustion engine, where they protect the moving parts from wear so that the engine can perform its service for a long time. Engine oils are more heat-resistant than transmission oils, as they are permanently exposed to high temperatures when driving. However, the combustion processes in the engine cause the oil to become increasingly contaminated over time. It must therefore be changed at regular intervals in order not to lose the wear protection and damage the engine.

In transmissions, things are not nearly as hot. Here, transmission oils take on the function of wear protection, corrosion protection and friction optimisation in order to secure power transmission in the long term and to improve driving comfort with smooth transmission shifts. Transmission oils do not have to be changed as often as engine oils. But recently since the significantly increased popularity of dual-clutch transmissions, the transmission oil has also become more important to drivers. Here, change intervals of around 60,000 km are intended. This is due to the friction processes when shifting transmissions in dual clutches. The transmission oil thermally degrades much more than in a manual gearstick. And the degradation products cause the oil to age more quickly.

Interior of a car
Engine and transmission require different lubricants

How can you tell engine oils and transmission oils apart?

Engine oil for the engine and transmission oil for the transmission - that sounds simple, but confusion occurs sometimes, which can cause damage.

This starts with the colour. The rumour persists that a transmission oil is always brighter than an engine oil. Due to increased efficiency requirements, today transmission oils have a significantly higher additive content than in the past. The more additives, the darker the lubricant and the more difficult it is to distinguish it from engine oil. Automatic transmission oils (ATF) are also no longer exclusively red in colour. For a few years now, ATFs have been available in different colours (red, blue, green, yellow). To make matters worse, even modern engine oils are now coloured according to OEM specifications (VW 50800/50900 = green). This means that a reference to the colour as a distinguishing feature is unfortunately no longer up to date.

Oils for cars have different colours
The colour of an oil does not determine its intended use

The viscosity is often used as the next characteristic. For automotive lubricants, viscosity is specified according to SAE classes. When directly comparing engine oil and transmission oil, the classification confuses the typical user. For example, an engine oil with SAE 10W-40 is almost twice as viscous as a transmission oil SAE 75W-80, although the numerical values tend to suggest the opposite. The type of specification appears the same, but it is done according to two different SAE standards. Transmission oils are usually thinner than engine oils, but fuel-efficient engine oils such as 0W-20 or even 0W-16 cannot even be distinguished from modern transmission oils in their viscosity without measuring technology.

Engine oil or transmission oil - pay attention to the label!

So even for experts, engine oils and transmission oils are no longer so easy to distinguish at first sight. ADDINOL therefore supports the end users with a new, clearer symbols and colouring on the labels of the transmission oils to make it easier to distinguish them from each other and from other lubricants. And our application technology will also be happy to answer your questions about automotive lubricants.


Christian Retschke

Christian Retschke

Head of Research and Development

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