94 RT/10 Black MAMBA
Enthusiast
flows just as well cold as it does warm? Why isn't it just a straight 30 weight oil for instance?
Why is synthetic oil graded as 10w** if it
- Thread starter 94 RT/10 Black MAMBA
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Tom F&L GoR
Enthusiast
The "W" number is determined by two laboratory bench tests conducted at temperatures well below 0C. A 10W-xx for instance, is tested at -25C (for the oil's effect on cranking speed) and -30C (for the oil's resistance to being sucked up the oil pump pickup tube.)
The second number is the oil's viscosity determined at 100C.
Part of the answer is that the use of the numbers themselves (like the "10" in the 10W-30, or the "30"...) don't have anything to do with the measurements. You don't get a "10" or a "30" value in the viscosity measurements listed above. In fact, each designates a range. The "30" for instance, means the viscosity at 100C is between 9.3 and 12.5 centistokes.
The other part of the answer is that even a synthetic does not really flow as well cold as well as it does warm. In fact, any oil, whether a synthetic or a mineral oil, with the same designation, i.e. 10W-30, will flow the same at the temperatures tested. Yes, at -25C, a mineral 10W-30 and a synthetic 10W-30, in the tests that relate to low temperature engine performance, are the same. If they weren't the same, they could not both be called a 10W-30.
OK, so what's the deal with a synthetic, then? The mineral base oil has a distribution of molecules, and the few larger than average ones cause the oil to turn to a waxy solid when it gets cold enough. A synthetic won't "freeze" like this. But this happens below the temperature range that the oil is designated for. So if both a mineral and synthetic oil are 10W-30s, then either could be used safely down to -25C, but at -35C the mineral oil will turn to jelly and the synthetic won't. Does that make the synthetic better at -25C?
The other thing with a synthetic is the ability to make wider range viscosity grades. For instance, the 5W-40, 10W-50, or 0W-30 grades are not technically easy or economically feasible with a mineral oil. In my opinion, this is a true real-world benefit in that you can satisfy your need for greater bearing protection with a thicker oil at high temperatures and still have very good low temperature starting characteristics.
For those that have trouble with the "all 10W-30s are alike" explanation, there are two answers - the 10W designation is also a range, so mineral oils may be at one end and synthetics at the other. (But if the synthetic were too much better, then it would have to be called by the next lower - a 5W-30.) The other answer is that pouring an oil out of the bottle may look different, but has been shown technically that it (and the official pour point test) has no prediction to how it performs in the engine. The two tests that are used (to predict cranking and sucking) have been shown year after year to be the relevant tests.
Good question.
The second number is the oil's viscosity determined at 100C.
Part of the answer is that the use of the numbers themselves (like the "10" in the 10W-30, or the "30"...) don't have anything to do with the measurements. You don't get a "10" or a "30" value in the viscosity measurements listed above. In fact, each designates a range. The "30" for instance, means the viscosity at 100C is between 9.3 and 12.5 centistokes.
The other part of the answer is that even a synthetic does not really flow as well cold as well as it does warm. In fact, any oil, whether a synthetic or a mineral oil, with the same designation, i.e. 10W-30, will flow the same at the temperatures tested. Yes, at -25C, a mineral 10W-30 and a synthetic 10W-30, in the tests that relate to low temperature engine performance, are the same. If they weren't the same, they could not both be called a 10W-30.
OK, so what's the deal with a synthetic, then? The mineral base oil has a distribution of molecules, and the few larger than average ones cause the oil to turn to a waxy solid when it gets cold enough. A synthetic won't "freeze" like this. But this happens below the temperature range that the oil is designated for. So if both a mineral and synthetic oil are 10W-30s, then either could be used safely down to -25C, but at -35C the mineral oil will turn to jelly and the synthetic won't. Does that make the synthetic better at -25C?
The other thing with a synthetic is the ability to make wider range viscosity grades. For instance, the 5W-40, 10W-50, or 0W-30 grades are not technically easy or economically feasible with a mineral oil. In my opinion, this is a true real-world benefit in that you can satisfy your need for greater bearing protection with a thicker oil at high temperatures and still have very good low temperature starting characteristics.
For those that have trouble with the "all 10W-30s are alike" explanation, there are two answers - the 10W designation is also a range, so mineral oils may be at one end and synthetics at the other. (But if the synthetic were too much better, then it would have to be called by the next lower - a 5W-30.) The other answer is that pouring an oil out of the bottle may look different, but has been shown technically that it (and the official pour point test) has no prediction to how it performs in the engine. The two tests that are used (to predict cranking and sucking) have been shown year after year to be the relevant tests.
Good question.
jimandela
Enthusiast
Tom, F&L GoR,
I love how complete your answers are.
thanks for the info.
JIM
I love how complete your answers are.
thanks for the info.
JIM
