Motor oils are becoming thinner and thinner and eventually motor oil as we know it may actually contain no actual oil. These are topics addressed by researchers from the Oil Laboratory at LIQUI MOLY. 

Oliver Kuhn, Deputy Head of the Oil Laboratory at LIQUI MOLY explains that the trend is towards ever thinner motor oils, in order to reduce fuel consumption and emissions. But the engine must also be designed for such an oil, otherwise there is a risk of expensive damage. However, motor oil cannot become arbitrarily thin, at least not if it is based on oil. 

Oliver says, “The viscosity of motor oil is indicated by two numbers, for example 5W-30. The first number with the “W” stands for the low-temperature viscosity, i.e. how fluid the oil is at low temperatures. The second number represents the high-temperature viscosity, i.e. how fluid the oil is at high temperatures. The following applies to both numbers: The higher it is, the more viscous, i.e. thicker the oil. And vice versa: The lower the number is, the thinner the oil.”

Oliver explains why oil is getting thinner, pointing out, “This is due to car manufacturers and their efforts to further reduce vehicle emissions. The thinner a motor oil is, the less force the engine needs to apply to pump it. This reduces fuel consumption. Thin oil is one of the many adjustments the auto makers make to increase the efficiency of their vehicles. Our task as an oil manufacturer is then to develop motor oils that are thin and still offer the required performance.”

Producing the required performance can only be achieved with state-of-the-art lubricant technology. Motor oils consist of base oil and the additive packages. In the past, the base oil was the most important element, but today it is the additive packages. They are not only responsible for the cleaning and corrosion protection with thin-bodied oils, but also for cooling and lubrication. The base oil, i.e. the actual oil, is now more of a fluid carrier for the additive packages, with almost a third of modern oils consisting of additive packages.

The right oil spec is now more vital than ever. If a thin oil is used in an incorrect application it will not be capable of bearing the load and then breaks down. A cracked oil film means significantly increased wear, which can extend to seized bearings. This, in turn, can lead to consequential damage up to major engine failure.

In the case of a thicker oil being used incorrectly, Oliver says, “The actual lubrication is less of a problem here, apart from the fact that fuel consumption increases. But to force the thick oil through the small oil passages designed for thin oil, the oil pump has to work more. As a result, it can become overloaded and fail. And then the engine is completely without lubrication.”

Oliver emphasises that the right oil for the application should always be selected. This can be found either in the car manual or by using the free oil guide at www.liqui-moly.com. 

So will the thin oil trend continue? Oliver says, “The lowest viscosity currently specified for motor oil is 0W-8, only used in Japan. This is almost a single-grade oil. In addition to lubrication, the difficulty here is above all evaporation, because the thinner an oil is, the easier it evaporates. With the 0W-8, this balance can just about be maintained. For even lower viscosities, it would probably require a completely different chemistry.”