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Did you ever wonder which to buy 15W40 or 10W40 or synthetic or not
Viscosity
This is simply the most important feature of any lubricating oil. It can be defined as a fluid's resistance to flow. As the temperature of an oil increases its viscosity decreases.
If an oil is to thin the lubricant film will break down under conditions of high stress. This allows metal to contact metal causing increases in friction, component damage and ultimately equipment failure. If the viscosity of the oil is too high then it is physically unable to squeeze between two metal surfaces.
The Society of Automotive Engineers Viscosity Classification
The terms SAE 10W-30 and SAE 15W-40 are widely used. How many people actually understand what these terms mean?
Firstly any viscosity grade should be proceeded by the initials SAE. This stands for the Society of Automotive Engineers and indicated that the following viscosity classification refers to their definitions. It should be noted that SAE is not a performance category it only refers to the viscosity of the oil. When comparing oils the reader should not only compare the SAE viscosity grades of two oils but also the engine performance classifications in order to be able to fully compare performance.
Let us consider the following: SAE 15W-40.
The fact that this classification has two parts; the 15W and the 40 indicates that the oil is a multigrade. The first number with the suffix 'W' indicates the oil's performance at low temperature. In fact the 'W' stands for winter. The lower the 'W' number the lower the viscosity of the oil. Therefore an SAE 5W oil is a lower viscosity oil than an SAE 10W oil.
The number after the W, in the above case '40'; gives a measure of the oil's viscosity at high temperature. Again the lower the number the thinner the oil is at high temperature. So an SAE 30 is a thinner, or less viscous, oil than an SAE 40.
A multigrade oil is an oil that has two parts such as SAE 15W-40, or 20W-50. A monograde oil only has one part, such as SAE 30, or SAE 40.
What is better a SAE 10W-40 or an SAE 15W-40?
Using the simple rules above it is clear to see that both of these oils have a similar high temperature viscosity as indicated by the '40'. However the 10W-40 is a thinner oil than the SAE 15W-40 at cold temperatures. Simply apply the rule that the lower the 'W'; number the thinner the oil. The SAE 10W is lower than the SAE 15W and hence is a thinner oil. Therefore in cold temperatures we can state that the SAE 10W-40 oil is better than the SAE 15W-40 oil. In winter the end user may experience a benefit by moving from an SAE 15W-40 oil to an SAE 10W-40 oil.
Can I use an SAE 10W-30 in summer
During summer when ambient temperatures are high the oil will tend to be thinner so a more viscous oil should be preferred. The SAE 10W-30 is a thin oil so generally speaking either an SAE 10W-40 or SAE 15W-40, both more viscous, could offer better engine protection. In summer is an SAE 10W type oil required? Probably not so the SAE 15W-40 would be the best recommendation. As a first step the manufacturer's recommendations should be followed.
In winter the situation is reversed and the SAE 10W-30 oil or the SAE 10W-40 should be favoured.
Mineral Oils Versus Synthetic Oils
There is much discussion about mineral oils versus synthetic oils and the relative performance of each type. It is clear that synthetic oils offer certain advantages over mineral oils in terms of low temperature performance, and high temperature oxidation stability but that is not the whole story. Synthetic oils are very expensive and properly formulated mineral oils are more than suitable for most engine applications. A synthetic oil can be considered for very cold temperatures, or for application that may need an outstanding level of oxidation protection but it should be remembered there is a significant cost. The question should always be asked: ‘Can I use a properly formulated mineral oil for this application?'
I got this from a Chevron site (and so that they dont sue let me say Chevron Oils are marvellous and we all love Chevron Oils).
Makes me laugh knowing the cheaper 10W40 stuff was better in the cold months
Viscosity
This is simply the most important feature of any lubricating oil. It can be defined as a fluid's resistance to flow. As the temperature of an oil increases its viscosity decreases.
If an oil is to thin the lubricant film will break down under conditions of high stress. This allows metal to contact metal causing increases in friction, component damage and ultimately equipment failure. If the viscosity of the oil is too high then it is physically unable to squeeze between two metal surfaces.
The Society of Automotive Engineers Viscosity Classification
The terms SAE 10W-30 and SAE 15W-40 are widely used. How many people actually understand what these terms mean?
Firstly any viscosity grade should be proceeded by the initials SAE. This stands for the Society of Automotive Engineers and indicated that the following viscosity classification refers to their definitions. It should be noted that SAE is not a performance category it only refers to the viscosity of the oil. When comparing oils the reader should not only compare the SAE viscosity grades of two oils but also the engine performance classifications in order to be able to fully compare performance.
Let us consider the following: SAE 15W-40.
The fact that this classification has two parts; the 15W and the 40 indicates that the oil is a multigrade. The first number with the suffix 'W' indicates the oil's performance at low temperature. In fact the 'W' stands for winter. The lower the 'W' number the lower the viscosity of the oil. Therefore an SAE 5W oil is a lower viscosity oil than an SAE 10W oil.
The number after the W, in the above case '40'; gives a measure of the oil's viscosity at high temperature. Again the lower the number the thinner the oil is at high temperature. So an SAE 30 is a thinner, or less viscous, oil than an SAE 40.
What is better a SAE 10W-40 or an SAE 15W-40?
Using the simple rules above it is clear to see that both of these oils have a similar high temperature viscosity as indicated by the '40'. However the 10W-40 is a thinner oil than the SAE 15W-40 at cold temperatures. Simply apply the rule that the lower the 'W'; number the thinner the oil. The SAE 10W is lower than the SAE 15W and hence is a thinner oil. Therefore in cold temperatures we can state that the SAE 10W-40 oil is better than the SAE 15W-40 oil. In winter the end user may experience a benefit by moving from an SAE 15W-40 oil to an SAE 10W-40 oil.
Can I use an SAE 10W-30 in summer
During summer when ambient temperatures are high the oil will tend to be thinner so a more viscous oil should be preferred. The SAE 10W-30 is a thin oil so generally speaking either an SAE 10W-40 or SAE 15W-40, both more viscous, could offer better engine protection. In summer is an SAE 10W type oil required? Probably not so the SAE 15W-40 would be the best recommendation. As a first step the manufacturer's recommendations should be followed.
In winter the situation is reversed and the SAE 10W-30 oil or the SAE 10W-40 should be favoured.
Mineral Oils Versus Synthetic Oils
There is much discussion about mineral oils versus synthetic oils and the relative performance of each type. It is clear that synthetic oils offer certain advantages over mineral oils in terms of low temperature performance, and high temperature oxidation stability but that is not the whole story. Synthetic oils are very expensive and properly formulated mineral oils are more than suitable for most engine applications. A synthetic oil can be considered for very cold temperatures, or for application that may need an outstanding level of oxidation protection but it should be remembered there is a significant cost. The question should always be asked: ‘Can I use a properly formulated mineral oil for this application?'
I got this from a Chevron site (and so that they dont sue let me say Chevron Oils are marvellous and we all love Chevron Oils).
Makes me laugh knowing the cheaper 10W40 stuff was better in the cold months
This IS just my opinion and others may disagree but an engine is an engine and generally suffer the same kind of issues it's just the degree of expense and chaos that varies!
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