Choosing lubricant for your engine

raised by the readers of the articles and as well as possible solutions to these problems.
First reader enquired whether you can mix oils, say Obel and Zim oil, as they are manufactured differently but appear to be equivalent in use.
The second reader brought up the issue of purpose and meaning of viscosity while the third one raised the issue of oil treatments or adding additives with the oil in the car? The fourth reader enquired about the kind and type of oil to use in her car?
This confirms the interactive approach in our articles in that we accommodate the views of the readers and hence give a broad answer to issues raised.
In the case of the first reader we agree that engine oils of similar quality and even of varying viscosities in our view can be mixed or co-mingled, without deterioration of the cooling, cleaning and lubricating properties of the oil.
Purely as an illustration assume you mix Mazoe Orange crush concentrate with Quench you will definitely get a certain flavour which invariably will not taste far better than the original Mazoe or Quench.
It is the same concern that conventional lubricants refined from mineral oil can also be mixed with synthetics, although the superior performance of the synthetic oil will be reduced or lessened by the dilution in the lower quality and performance oils.
The mixture of oils cannot cause damage to motor or light truck engines. This aspect will be felt later and not immediate.
We generally encourage use of particular oil notwithstanding that while that can be done let’s assume you change your oil at 5 000 kilometres and you top up periodically with 500 mls and by the time you have done that ten times you would have actually done an oil change.
Unless you change the oil filter by that time you would not have accomplished change as there are still contaminants in your oil which will affect it and clog the oil filter immediately.
We believe at that interval change your oil with the recommended one as per manufacturer’s handbook or per advice of the authorised dealers of that particular car. The golden rule is always follow the manufacturer’s instructions save on recognising the weather and temperature for Europe and Zimbabwe.
For instance the Mazda BT-50 specifically address the types of oil to use for various regions such as Europe, Russia, Israel and Africa.
In case of Zimbabwe they specify the following for diesel engines 5W30, 10W40 but we believe you can use 15W40 although they recommend it for petrol engines.
The response to the second reader on viscosity is proffered as being a measurement of the resistance to flow of motor oil; the higher the number of viscosity, the greater the resistance of oil to flow, and the greater the thickness of oil. Engine oil viscosity changes with temperature which is why multi-viscosity oils are better for engine performance across a wide variety of temperatures.
Let’s take an example of 15W50 and 15W40. Whenever you see the word “W” take it to mean winter but rather multigrade in that it can operate in both cold and hot temperatures as opposed to a monograde, hence in above case 15W represents the ability of the oil to flow at low temperatures.
The lower the number, the greater the ability of the lubricant to move to critical engine parts in low temperature operation.
Also note that most wear and tear occur at start up of engines in that the faster the oil gets to the moving parts the better and the slower it is means that these parts are exposed to lack of oil and the engine can cease during this process.
The 50 represents the ability of the oil to stand up to high engine operating conditions.
The higher the number the greater the ability of the oil to form a protective film on vital engine parts under extremely hot engine operation.
Therefore it follows then that the 40 cannot perform far better than the 50 on operating conditions. There is a tendency among buyers of oils not to appreciate these codes and you will find one using SAE50 as being the same as 15W50.
To achieve these characteristics the oils should possess properties that define and determine these functions.
For an oil to perform perfectly well it must be able to maintain its initial property levels by coping or resisting the heat that is generated by the equipment or machinery.
For this reason most oils must be highly oxidation resistant and in addition to these lubricants also act as heat transfer mediums and their effectiveness will depend on their viscosity, to determine the speed at which the oil takes the heat away from the frictional sources to the water cooling system.
The oil also has to have good thermal conductivity (the rate of heat absorption) and its specific heat (maintenance level of heat).
In some countries where cold temperatures are experienced the oil may lose its fluidity making it difficult to lubricate during start up and for this reason oils must be able to resist the cold conditions by maintaining their fluidity in freezing temperatures. In other words the oil must have a low pour point (the point as which oil ceases to flow).
This is a vital component of the oil in applications that generate cold temperatures of which are the refrigerators or acclimatisers.
The oil must be able to work perfectly well under cold conditions without losing its fluidity.
In applications like the steam turbines where there is the possibility of oil mixing up with water the oil should readily be able to separate quickly with the water, that is, the oil should have good demulsibilty (the rate at which water separates from oil.
The issue raised by the third reader on use of oil treatment, we are of the view that most oils manufactured by established companies around the world are made to meet the demanding specifications of international cars and light truck manufactures.
The tests for these companies are very severe and motor oils are designed to supply all the lubrication performance necessary for all possible operating conditions. The additives or elements that are sold in the shops, in most cases, could possibly degrade viscosity and storage stability and reduce anti-oxidation and thermal stability characteristics.
We do not recommend such use to oils. If the performance is compromised you could have bought a sub standard oil, an issue we have highlighted in our previous articles.
The last point by the fourth reader on what oil to use in your car, our recommendation is that at all times be led by the instructions contained in the manufacturer’s hand book.
This will tell you the length and times between oil change and what type of oil to use.
In the absence of that contact your service provider. Very few motorists utilise the engine oil analysis to check the status of their engine.
One person had this to raise with us and stated on the real benefit of this analysis.
He enquired as to the purpose and befits of tribology which we advised being confirmation of the analysis on the state of your engine. His argument being he will be told that the oil needs change and that it was the appropriate timing for that a thing he is aware.
His view was that it was a waste of his hard-earned money. We encouraged him to have his oil analysed periodically and test the oil’s viscosity and acid content using a spectrometre a device that burns the particular oil to identify the impurities.
We encourage motorist to avail themselves with service moreso to large transport operators we believe there is need to constantly have your oils checked.
Possible tit bit for small cars
You can get away with this if you religiously follow the manufacturer’s handbook recommendations in this regard and invariably will save your self unnecessary bills.
l Lets meet again next week and contact us on 751614 and or through G.Mbeya on 0774215 505 or [email protected]. PROUDLY ZIMBABWEAN