Category: Automotive

TBN decrease


The TBN has dropped significantly, can I still use the oil?

The TBN (Total Base Number) is usually seen in diesel engines. Most modern (smaller) diesel engines have TBNs within the range of 9-15 (especially if they are using ULSD).

The TBN gets depleted when the acids in the oil start to increase.

Typically, higher sulphur levels in the fuel produce more acids. As such, as the sulphur level increases, so does the TBN level.

For instance, in power plants that use larger (older) diesel engines that require HSFO (High Sulphur Fuel Oil, 3.5% sulphur), the TBN of the lubricant can be as much as 50. Here are the different types of fuel and their sulphur ratings:

  • HFSO (High Sulphur Fuel Oil): 3.5%
  • LSFO (Low Sulphur Fuel Oil): 1.0%
  • ULSFO (Ultra Low Sulphur Fuel Oil): 0.1%


With IMO 2020, the cap has been placed on sulphur in fuel to 0.5% for marine vessels. While this cap has not yet been translated to land applications, due to the demand for HSFO declining there may be a shift to ULSFO in land based applications in the not so distant future.


Ideally, if your TBN level gets depleted by 50% then there is a cause for concern and the oil should be changed or topped up with new oil (depending on which is more convenient).

If your TBN levels get to 50% in a very short time, you may want to investigate the reasons behind the value dropping so significantly in such a short time (perhaps fuel dilution or thermal cracking?).

Always investigate the reasons behind unexpected results as these will continue to impact your lubricant in the future.

Mixing oils


Can I mix hydraulic oils with engine oils?

Oils should never be mixed!

Every oil is designed with its application in mind. As such, they are blended with varying concentrations and types of additives. For instance, a typical engine oil has at least 30% additives while a turbine oil may have only 1% additive.

Hydraulic oils are designed for applications where power has to be transmitted through the lubricant. On the other hand, engine oils are designed to withstand varying temperatures (gasoline engines have a different temperature range compared to diesel engines. Diesel engines generally run at higher temperatures than gasoline engines).

Always pay particular attention to what the OEM recommends. Usually, the OEM will recommend that a lubricant meets a particular global standard (API SN or CK4). These standards were developed to ensure the best performance of an engine and should be adhered to when choosing lubricants.

Multigrade vs Monograde


Why use multigrade instead of monograde oils?

A monograde oil does not provide the same level of protection on start-up as a multigrade oil.

With the multigrade oil, it is designed to reduce the time it takes to get from the bottom of the sump to the top of the engine (this is indicated by the number in front of the “w”).

However, the monograde oils have not been adapted for this type of technology. Thus, it takes longer to get to the top of the engine and to all the components compared to a multigrade oil.

Most wear occurs on start-up. Before we start the car on a morning, all of the oil is at the bottom of the sump, so it takes some time to get to the top and the other components. However, once we start the engine, all the parts will begin moving. If they are moving without any lubrication, then a significant amount of wear will occur!

Typically, when driving, we start the car, go to our destination and stop. Then come back and start the car again. During this time, the oil would have drained back to the bottom of the sump and now has to get back to the top. Before it gets to the components, these are still moving without lubrication, inducing wear! If we think of the number of times that we start and stop for the day (or for the month!), we will realize the amount of wear that we put our engines through.

Hence, this is one of the main reasons, that we choose multigrades over monogrades.

That “w”!


What does the “w” stand for in multigrade oils?

The “w” stands for winter.

Let’s go back a bit. We weren’t always as advanced in lubricant technology as we are today. For instance, if we left an ice tray filled with water on the table, what would happen? It would remain in that state of water. Now, if we placed that in the freezer, the water would turn into ice.

Similarly, before we advanced lubrication technology, there was one oil to be used for the Summer and one for the Winter. During the summer, the temperatures were higher and during the winter the temperatures were lower.

The “w” helps us to understand that this is the measurement related to how an oil flows at a cold temperature (or on start-up). It does not mean that you can only use an oil with a “w” in countries that experience winter!

The lower the number is in front of the “w”, the faster the oil flows on start-up. When we start our cars on a morning, all of the oil is at the bottom of the sump. It will take some time before the oil gets from the bottom to the top of the engine.

However, all of the parts in the engine are moving before they get the oil. Thus, it is critical to get the oil to them in the shortest time possible. The lower the number in front of the “w”, the faster the oil takes to get to the top of the engine (this will reduce the amount of wear that occurs).

Quick Tip: Zero (0) does not mean that there is no protection on start up, it means that it will get to the components faster than all the other grades (like a 0w20).


What about the number after the “w”?

This is the number that represents the viscosity of the oil at operating temperature. When the engine begins operating this is the viscosity that flows through all of the lines and components continuously. As we mentioned in an earlier post, the value has decreased in recent times (some going as low as 0w16!) due to the lines being thinner, which is ideal for lower viscosities.

Recommended oil – Automotive


What type of oil should I use in my car?

Always follow what the OEM recommends! A quick google search can help you find the required lubricant if you don’t have the owner’s manual.

Most modern vehicles use lighter weight oils compared to older vehicles. Let’s think about cars back in 1950. They were larger, with big engines. With a big engine, it would mean that the lines carrying the oil would be larger. Thus, a heavier oil (50 weight) would be the most appropriate.

Now, fast forward to cars today. The engines are smaller, (albeit with a lot more horsepower as well!). If the size of the engine has changed, then the size of the lines carrying the lubricant will change as well. These lines will get smaller. If the lines are smaller, then the liquid that has to flow through them, should be lighter (thinner).

We can use an analogy of a straw trying to pull up molasses.

With a large straw, we could pull up the molasses faster than with a thinner straw. This is similar to the older cars, they would have thicker “straws” (lines) that would have allowed them to adequately pump the lubricant.

In the newer cars, the straw has gotten thinner, so it can’t pull up the molasses anymore. If we tried to pull up water instead, it would definitely flow faster than the molasses and not have as much strain on the person pulling up the water (pump in the engine). Hence, lighter oils are used in modern cars.

Most recommendations can be found by contacting the OEM or even doing a bit of Google searching with the year of manufacture for the car and of course the model.