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Oil lubricates all the moving parts of the engine, by providing a protective film that reduces wear and friction, meaning more power is transferred to the wheels. It also helps keep engine parts clean and free from harmful deposits, protect against rust and corrosion. Finally, oil cools the engine, by removing excessive heat from the combustion area and down into the oil pan.

Oil Bases

Mineral Oils

Mineral oils are conventional oils that man used for decades, which are produced by crude oil distillation and then mixed with some additives like detergents, viscosity improvers and anti-wear agents. They are relatively inexpensive and deliver average performances.

Synthetic Oils

Synthetic oils are completely man-made at the laboratories by complex chemical processes, and they are more expensive. Synthetic oils have better thermal strength, meaning they are capable of maintaining their viscosity for longer periods of use and under much greater temperatures than conventional mineral oils.

Semi-Synthetic Oils

The other type is semi-synthetic, the blend of the two (usually 70 to 80% mineral oil and 20 to 30% synthetic oil).

What is Viscosity and Viscosity Index?

Viscosity is, simply the measure of an oil's thickness and ability to flow at certain temperatures. Generally, the thicker an oil, the higher its viscosity and the thinner an oil the lower its viscosity. This property of oils is represented with a grade called Viscosity index (VI). The Viscosity Index tells us how much the oil will thin when it is subject to heat. The higher the index, the less an oil will thin when it is subject to heat. Lower numbers indicate thinner oil (low viscosity) and higher numbers indicate thicker oil (high viscosity). The Viscosity Index of an oil determines how it reacts under certain conditions. An oil with a too high viscosity may not pump to the proper parts of your engine especially at low temperatures, and the film may tear at high RPM. An oil with a too low viscosity can lose its film strength at high temperatures.

Single (Mono) and Multi-Grade (Multi Viscosity) Oils

There are two grades of motor oils, single grade and multi-grade. Monograde oils are usually used when the operating temperature is relatively stable (or for specific applications), meaning they can not meet both winter and summer requirements.

Multi-Grade oils are that we use today, which are suitable for use at different temperatures, meaning they are able to meet both winter and summer requirements. A heavy base oil would turn to jelly in cold temperatures if some polymers are not added. To prevent this, multi viscosity oils are produced by adding some polymers to a lighter base, thus these oils are thin enough to work at cold temperatures, and safe enough to work at high temperatures.

What are the advantages of Multi Viscosity Oils?

A multigrade oil is one whose properties have been artificially modified to reduce changes in its viscosity with temperature changes. A multigrade oil will be more fluid at low temperatures and thicker at high temperatures than a monograde oil.

That means that when the vehicle is not being used (for several hours), the engine oil sinks in the crankcase so that, on starting, it takes a certain amount of time (a few microseconds) to again reach all parts of the engine that need to be lubricated. Since a multigrade oil is more fluid at low temperatures, it reaches the various engine components more quickly than a monograde oil, thereby reducing wear on starting.

Multigrade oils usually produce fuel savings of 1.5 to 3% in comparison to monograde oils.

Multigrade oils provide better engine protection at low and high temperatures than monograde oils, in that they maintain optimum viscosity over the engine operating temperature range.

How do Multi Viscosity Oils Work?

A VI (Viscosity Index) improver can be thought of as a very long string which at low temperatures is tightly coiled into a small ball and floats suspended in the oil with little effect on the viscosity of the oil. At high temperatures this ball expands and uncoils and encloses a much larger volume of oil within its structure. This effectively prevents the oil from thinning because of the greater volume taken up by the expanded ***** of VI improver molecules.

At cold temperatures the polymers are coiled up and allow the oil to flow as the low number indicate (like in 5W-30). As the oil warms up the polymers begin to unwind into long chains and prevent the oil from thinning. Thus, a 5W base oil doesn't thin more than a 30 weight would when it is hot. This is like using two different oils, one for winter and one for summer in one. In the winter base your choice must be the lowest temperature you expect, and in the summer base the highest. The narrowest span with a more heavy base is better if your temperature zone allows, cause a wide span means more polymers, and more polymers are not good for your engine.

Choosing Viscosity Grade

The most known engine oil viscosity classifications are as follows:

SAE (Society of Automotive Engineers) Classification:

The SAE classifications characterizes the viscosity at low and high temperature of the lubricant. The grade is given by two numbers separated by the letter W (meaning winter).

The first number, followed by W represents the low temperature viscosity, 5W, 10W, 15W... the lower this number, the more fluid at low temperature the oils, the easier the engine starts.

The second number gives the high temperature viscosity: 30, 40, 50. The higher this number, the more viscous the oil when hot.

Below are some examples on choosing engine oil by expected outdoor temperature:
If lowest expected outdoor temperature is: Typical SAE viscosity grades for passenger cars:
0 degrees Celsius (32F) 5W-30 10W-30 10W-40 20W-50
-18 C (0F) 5W-30 10W-30 10W-40
below -18 C 5W-30

In the winter base your choice must be the lowest temperature you expect, and in the summer base the highest. The narrowest span with a more heavy base is better if your temperature zone allows, cause a wide span means more polymers, and more polymers are not good for your engine.

The other known classifications are:

API (American Petroleum Institute) Classification:

Oil performance is expressed by two letters. The first letter indicates whether the oil is for gasoline (S) or diesel (C) engines. The second letter specifies the level of technical performance within the relevant group: A for the minimum level for both gasoline and diesel, and J (gasoline) and F (diesel) for the highest level.

Gasoline: (min. performance) SA..SB..SC..SD..SE..SF..SG..SH..SJ (max. performance)

Diesel: (min. performance) CA..CB..CC..CD..CE..CF (max. performance)

ACEA (Association of European Car Manufacturers) Classification:

Oil performance is described by a letter followed by a number.

ACEA standards are divided into three categories:

* A for gasoline engines
* B for diesel car engines
* E for diesel engines for commercial vehicles and trucks


Levels of lubricants performance are expressed by a following number:

* 1 for fuel-economy oils
* 2 for general purpose oils, and
* 3 for high performance oils


Example: A1 describes a fuel-economy gasoline engine oil, and A3 describes a high-performance gasoline engine oil.

The proper viscosity grade to use depends on many factors such as ambient temperature, miles on the engine, bearing and piston clearances, and type of service. A general rule of lubrication is to use the lowest viscosity possible which will provide the proper separation of metal. Anything more than this minimum will increase power loss due to friction and will reduce the pump ability of the oil at all temperatures. However, one must consider synthetics differently when determining viscosity requirements.

Mixing Two Other Types

It is said synthetic oils are compatible with the conventional mineral oils, thus it is safe to mix two different types, but for sealing purposes and the final performance of your engine i suggest you choose one at the beginning, and never change your oil type.. It is known that the content of mineral oils are different than synthetic oils, and mineral oil soaked gaskets and seals have been known to leak when exposed to synthetic oils. So, you may think using flushing oil first, before switching another type as some people suggest. Yes, the flushing oil removes all the deposits and dissolves all the mineral oil deposits in your engine and you may think everything is ok for switching to synthetic oil, but using a thin oil for flushing may remove deposits that built-in time and work for sealing your rings and gasgets. It is known that engines over 250,000 km worked without a problem, but when flushed it failed in a month. So choose one at the very beginning, flush your engine if necessary, and never change the oil type. Only move to a different weight in the same type, if it’s necessary because of a considerable change in temperature zone, cause the viscosity must be adapted to the conditions in which the vehicle is used, the environment and the climatic conditions.

Are Additives Useful?

There are different kinds of engine oil additives today, and a lot of adds for them on TV especially at night, telling their product is the best. Now imagine that.. Oil companies spend millions of dollars each year to improve their formulas, and so are the automobile manufacturers. First, can you believe that there is a magic formula, and oil companies that spend millions of dollars to R&D for years laboring the best chemical engineers especially for that reason couldn't find that magic formula, and only that additive manufacturers found? Second, if they really work and not harmful to your engine, why automobile manufacturers put one bottle of them to every car they produce? Thus, they can improve their engine's performance and reduce fuel consumption. Third, none of that famous oil additives carry the name of the major oil companies.

Teflon

Some oil additives may seem working at the very beginning, but those which contain particles like Teflon may block the oil filter and the oil ways of your engine. DuPont Chemical Company, inventor of PTFE and holder of the trademarks of Teflon says "Teflon is not useful as an ingredient in oil additives or oils used for internal combustion engines".

Zinc

Another kind of engine oil additive is that the one containing zinc. Zinc is used as an anti-wear additive in oils and useful when there is really a metal to metal contact in your engine, which should normally never occur under normal conditions. Every major brand engine oil already contains enough zinc, so why add more? More zinc doesn't give you more protection, it just prolongs the protection if the rate of metal-to-metal contact is abnormally high. Adding a can of zinc-reach additive will just work for forming deposits on your valves, and will cause spark plug fouling, believe me..

What Is The Relationship Between a Lubricant And Fuel Consumption?

The viscosity of an oil comes from the internal friction within the oil: the more viscous the oil, the more internal friction. By using a low viscosity oil (generally SAE 0W-30) in an engine, the losses caused by friction internal to the lubricant are reduced: the petrol consumption is therefore enhanced by a few percent. However caution should be used, this type of oil is not suitable for all engines.

Are Dirty Oils a Sign Of Engine Problems?

Dirty oil is not a sign of engine problems. In fact, it's a good sign. It means your oil is doing its job: picking up deposits and keeping them suspended so they can't collect on engine parts. When you change that dirty oil (and your oil filter), you remove the deposits.

How To Check The Engine Oil Level?

In order to get a correct reading of the oil levels, the engine should be slightly warmed. Check your oil on level ground. Wait at least 5 minutes after switching off the engine. Remove the dipstick. Wipe it. Replace and wait a few seconds before removing it again. Check the level with reference to the MIN and MAX marks. You should add oil if the level is below the MAX mark. Add the oil a little at a time. Recheck the level and repeat the operation until it reaches the MAX mark. But don't go above it! Replace the dipstick. Recheck your oil level about every 2000 km.

Result

* Every oil is blended for the optimum result, so adding an additive can result in harmful mixtures. Just buy the best brand on the shelf, never change it, and when you start your engine, let it idle for about 15 seconds before moving off, thus you can be sure that the oil is warmed up a little bit and can reach to the most vital areas of your engine before you push the accelerator pedal. Every manufacturer today tell you not to let the engine warm-up before driving off, but they mean don't let it reach to normal working temperature.. You can probably add another 100,000 km to your engine's life without one bottle of additive by doing this.
* Use an oil that can suit your performance needs. Synthetic oils are more expensive than minerals, but they last longer and provide more protection and better performance especially on sports cars.
* Choose the narrowest suitable span for your needs. A wider span means more polymers, and more polymers are not good for your engine. (Ex. 10W-30 or 10W-40? 10W-30 has a narrower span than 10W-40, thus requires few polymers. 10W-40 requires more polymers than 10W-30 to work at hot temp).
* Don’t make a choice of a lighter base if there’s no need in the name of temperature. (Ex.10W-40 or 20W-50? 10W-40 has the same 30 point spread with 20W-50, but 20W-50 has a 20W base which is heavier than 10W, thus a 20W-50 oil needs less polymers than 10w-40).
* You should change your oil filter at every oil change. The oil filter is a strainer that filters out the solid particles of dirt and metal that are picked up by the circulating motor oil. When the filter becomes clogged, a bypass valve allows these contaminants to continue circulating with the oil in the engine, damaging engine parts and creating sludge. Since there's no light on your vehicle's instrument panel to indicate a plugged filter, it's inexpensive insurance to change the filter every time you change your oil.
* In any case, it is important to change the oil at least once a year.

found this on the EC compacts site

shoptek

VERY informative---thank you! :cheers: