Density Of Engine Oil – Everything You Need to Know!

Let’s start by saying that the oil density intensifies with oxidation progress. There is no doubt that density plays a very important role in how lubricant and the machine work. It is said that most systems are designed in a such unique way to pump a liquid of a specific thickness.

As the density changes, you can then expect the pump efficiency to also change as well. So, if it’s a case where you don’t understand the density of engine oil, then it is rare for your engine to perform as you’d like it to. This is why knowing the engine oil density is very important and is something you should know.

You may already know about viscosity since it helps to calculate how oil can flow easily at a certain temperature.

What is Oil Density?

Density Of Engine Oil

Oil density is known to be a very essential property not only when it comes to lubricants but in all fluids. For example, as the density of a lubricant increases, then you can expect the fluid to become thicker. At this point, it enhances the time it takes for particles to settle out of suspension. But, before moving forward, it is very important that you know what density is.

The density is also known as the specific mass, it is said to be mass per unit volume. In the shorter term, density is considered as mass divided by volume.

The density formula is d = M/V, which means d is density, M is mass, and v is volume.

The thing is that the fluid density may change for several reasons and can even convert the errors of both values of consistency. Apart from that, the common word in relation to density is specific gravity in conjunction – the relationship of water with density.

It’s safe to say that density is considered to be a specific gravity and is said to be related to the viscosity of the oil. In terms of water, it comes with much density from engine oil and is known to work with a lower viscosity. Based on studies done by the Association of Automotive Engineers standard, the oil viscosity is determined on the market.

Measuring Density of Lubricants:

You will find that the density of most oils will range between 700 and 950 kilograms per cubic meter (kg/m3). When it comes to oils, it is usually indicated in the temperature of +15°C or +20°C, in units kg/m3. On the other hand, water is known to have a density of 1,000 kg/m3. What this means is that most oils will actually float on water as they are lighter by volume. If it were a case where the density of an object is less than that of water, then you can expect that object to float.

This is why if your lube system has a moisture problem at the bottom of the sump, the water will eventually settle. However, this is not always the case, as some Group IV base oils can have a higher density than water and for that reason, the oil will sink into the water.

Density Temperature Relation

When it comes to temperature, it is what the density is dependent on. Even though you’ll find that the dependency is much smaller compared to lubricant viscosity. Below we have put together an experimental formula that you can use to calculate the density change with temperature.

P= PT1 + ap (T1 + T) where AP = 0.65 for 831KG/m3 < p < 950 kg/ m3 and AP = 0.6 for 950kg/m3 <= p < 1000kg/m3.

Based on the formula, you’ll be able to tell that the experimental relation is only suitable for the oils with densities in a specific range. However, these ranges can work with most (860-980) lubricating oils.

The Density of Engine Oil:

p=0.8848 g/cm3

p=884.8 kg/m3

p=0.8848 g/ml

p=884.8 g/L

p=55.2363 lb/ft3

What is the Density of 15W-40 Engine Oil?

The density of 15W-40 engine oil is considered to weigh roughly 0.8725 gm per cubic cm or 872.5 kg per cubic meter. Another thing to know is that the SAE 15W-40 engine oil density is equal to 872.5kg/m3; at 30°C or 303.15k at regular atmospheric pressure. When it comes to the US customary or imperial measurement system, the density = 54.4684 pounds per cubic foot.

Density Test Standard

ASTM D5002-19: Standard Test Method for Density, Relative Density, and API Gravity of Crude Oils by Digital Density Analyser. This testing process is said to cover the determination of the API gravity of crude oils, relative density, and density.

This method can handle fluids between 15°C and 35°C. This test is capable of processing and suits crude oils with high vapor pressures. During the analysis of density, the analyzer will take proper precautions just to prevent vapor loss from occurring.

ASTM D1298-12: Standard Test Method for Density, Relative Density (Specific Gravity), or API Gravity of Crude Petroleum and Liquid Petroleum Products by Hydrometer Method. With that said, this test process is capable of covering the determination of the laboratory by simply applying a glass hydrometer.

You will usually find these test processes to perform this with a calculation of relative density, API gravity, and density. At existing temperatures, the values are known to be assured and corrected to 60°F or 15°C by calculations and international tables.


As you can see, engine oil density is based on the physical volume and mass rate. With consistency, the parameter is known to come with direct dependence on temperatures. However, when it comes to hydraulic transmission, the engine oil density is what provides the power.