22. What is a base oil?

Base Oil (sometimes also called base stock) is the name given to the main liquid component (or components) of a lubricant. It is. Base oils are mineral (or petroleum) or synthetic in origin, although vegetable oil-derived stocks may be used for specialized applications. The base stock provides the basic lubricating requirements of a lubricant.; i.e. the "oiliness"

However, in most modern lubricants a base oil mixture alone is insufficient to deliver the technical performance characteristics required and to keep the product from rapid degradation in use.  Therefore the lubricant manufacturer will mix the base oils with a variety of different additives, each chosen to impart additional performance benefits to the finished oil.

23. What are the different kinds of base oils?

Base oils are be classified by both viscosity and their generic chemical composition, itself a function of the original crude oil and/or the refining process. Depending on the proportions of hydrocarbon molecule type: base oils can be either paraffinic, naphthenic or aromatic in nature. There are several widely used viscosity classifications, of which the term ‘solvent neutral' is the most common, e.g. SN 150 and SN 500, where the number represents the SUS viscosity (measured in Saybolt Universal Seconds at 40 C).  Base oils are also classified by their viscosity index (a calculated figure based on the viscosities measured at both 40 and 100 C). Thus oils are either Low Viscosity Index (LVIs) or Medium Viscosity Index (MVIs), High Viscosity Index (HVIs) or extra High Viscosity Index (XHVIs). The higher the viscosity index, the less the oil will ‘thin down' upon heating, and the less it will ‘thicken up' upon cooling.

Base oils are also be defined by the type of refining process used: solvent extraction (for solvent neutral oils) is widely used, but more highly refined oils can be made by a hydro-finishing process or by hydro-cracking.

24. What are synthetic base oils ?

 
Synthetic base oils are chemicals that have been made, or synthesized, by combining several smaller molecules together. There are several different types, each with its own suite of physical and chemical properties, and each ideal for a selected set of uses in lubrication. Because these are ‘made to design', and are usually quite pure in composition, the lubricants they are used in can have specific properties which cannot easily be achieved though the use of mineral base oils. This advantage, though, comes at a higher price.

25. Are synthetic oils better than conventional motor oils ?

In most cases the answer is "yes". Synthetic oils are manmade lubricants which were originally created for jet aircraft engines. They have a wide range of performance and can protect engine at very high and very oil temperature conditions. In other words, they have exceptional thermal stability.

The main disadvantage of synthetic lubricants is that they are inherently more expensive than mineral oils. This restricts their use to specialty oils and greases which command premium prices. Coincidentally, oil marketers therefore ensure that their synthetic oils are also capable of the highest performance possible

26. Where are these synthetic base oils used?

 
The main advantages of the synthetic oils are in their high viscosity indexes, higher flash points, lower pour points and very low volatility (tendency to evaporate at higher temperatures) This makes them valuable blending components when compounding for extreme service at both high and low temperatures.

27. What are hydro finished base stocks? What other kinds of base oils are available in the world?

The list is extensive. Hydro-finished base oils are mineral oils that have been subjected to a light hydrogenation treatment to remove certain impurities that could affect the oil's chemical stability. There is a long list of synthetic fluids used to make lubricants; poly-alpha-olefins, long chain organic esters, phosphate esters, poly-glycols, poly-alkylbenzenes are the most common.

New refineries are being built in which natural gas (methane) is converted into liquid fuels (gasoline, diesel fuel), and a useful by-product will be heavier hydrocarbon molecules which can be used in lubricants. These gas-to-liquid base stocks are expected to have properties similar to some of the synthetic molecules now used, but be available at a much lower cost.

28. Can synthetic oils be used for longer periods, or will they prolong the engine’s life?

It is always best to follow the vehicle manufacturer's (the OEM's) recommendation for oil drain periods. Some OEMs do permit extended drain intervals when high quality, high performance synthetic oils are used. This is often done in combination with extended vehicle and engine service intervals, as it is in the OEM's interest to ensure the engine and the oil will require servicing after longer and longer intervals.

29. Why are additives used in lubricating oil?

Additives are used in lubricating oil to change or alter or enhance its properties. Base oil as such cannot be used in most of the present-day lubricating applications. Their properties - like resistance to heat, oxygen, wear etc - have to be increased. This increment is done with the use of these additives. To increase the resistance to oxidation, we add 'antioxidants', to increase resistance to wear, we add 'anti-wear additives'

30. What are these additives ?

The list below covers most of the additives used. You can see that lubricant formulation is a real science as there are many components and variables, all of which must be balanced out to make a well-rounded product, which is then proven by a series of rigorous tests.