Some gyan:
SYNTHETIC vs. MINERAL (battle of the advertisers)
The differences between these types of oils are all in the molecular makeup. Synthetic oil has a very consistent molecule size which gives the oil very good and consistent properties. Mineral oil being a product of nature has lots of different sized molecules in its makeup. The advantage of synthetic is that it potentially has a more stable suite of properties that can be tailored to a wider range of applications. This is why you can now find oils that can cover huge viscosity ranges such as 15W40 and even OW30! There are definite advantages to this ability but careful consideration of application is necessary.
To review some of the oil jargon let's look at what the numbers and letters mean that I just referred to. Viscosity is determined by measuring the flow properties at a fixed temperature. A base number is set as standard then relative flow numbers are assigned to describe the relative viscosity of the oil being measured. The lower the number the "lighter" the oil is. That means it flows much easier at the same temperature than one with a higher viscosity rating. There are single viscosity oils so it is simple to understand that 10 weight oil flows easier than a 30 weight oil under that same temperature circumstances. Multigrade oil is what has become possible due to additive packages and has been further enhanced by synthetic oils. A number such as 10 W 30 means that the oil has variable properties between this range of viscosities. The best thing about this is that it can compensate (within its designed capability) for the negative effects of temperature on viscosity. High temperatures drive viscosities down but multigrade oils have the ability, due to their additives, to compensate. So back to our 10 W 30 example. The 10 means that it has the viscosity (flow properties) of a single grade 10 weight oil at LOW temperatures. The "W" following the first number is the convention that verifies this tested ability. The last number is the viscosity rating at HIGH temperatures. The working temperature range is approximately between 0 and 100 degrees Celsius.Things go out of whack above and below. Above 100 degrees C. the viscosity begins to lower as it would with single grade oil. The viscosity can be lowered by as much as 50% for higher than 100 deg. C temperatures.
You need "thinner' oils like 10 or multigrade with 5W or 10W when the engine temperature is low particularly here in Canada where we can see quite cold temperatures even in good driving months, never mind winter. This low viscosity allows the engine to receive vital lubrication. Imagine trying to pump grease versus olive oil. A 30, or worse, a 50 weight oil would look, feel and work just like grease at 0 degrees Celsius. Your engine will suffer. Olive oil would in fact work better under these conditions, but not for long!
The need to have good lubricating properties at low temperatures but then have good lubricating properties at high temperatures is what has stimulated the development of multi grade oils. So our 10 W 30 has the easy flowing viscosity of a 10 weight oil when cold and then the lubricating properties of 30 weight oil when it is hot. Just what we need in a country like ours where the temperatures are widely variable at nearly anytime of the year.
Engine design has a lot to do with which grade and which type of oil you should choose. If the engine was designed to work with a single grade mineral oil with its multi sized molecules and low or high single grade viscosities then using something "better" may not have any significant benefits. If however your engine is designed to exploit the benefits of multi grade fully synthetic oil then that is exactly what you should be using. Therefore putting new multi viscosity synthetic oil in your old iron horse could present a problem and vice versa.
Advertisers are not engine designers. They publish brochures to make people think that they are getting better value or in some case something for nothing. Go by the manufacturers recommendations. They are the ones who have designed and extensively tested the engine and know what it needs.
Source: Lubrication Post EDITED deleted since it contained various [FONT], [COLOR] and [SIZE] tags. Posting with such text formatting should be avoided on Team-BHP as it is inconvenient for members to read post. Kindly go through Announcements section before proceeding.
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Last edited by Jaggu : 15th August 2008 at 00:37.
Reason: Font and fomratting tags!!
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