# Oil viscosity units

• posted

I sincerely hope that one (or more) of you can answer this seemingly simple question.

Domestic heating oil is known variously as paraffin, kerosene and

28-second oil, and diesel fuel as 35-second oil. I have always assumed that the numbers 28 and 35 referred to some system of viscosity measurement, but which one? Google isn't terribly helpful, other than to tell me that there are more systems of measuring viscosity than I ever dreamt of!

TIA

Pete

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Vaguely how long it takes a given quanity of the oil to flow through a given sized hole in a given container at given temperature. Not sure if the head of oil above the hole has to be maintained or not and what all those "givens" are I haven't clue...

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I think this method of viscosity measurement is the Redwood scale.

In message , Peter Scales writes

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As far as I know it is the time taken for a specific measure of fluid to flow through a calibrated standard oriface. Therefore, 28 second heating oil is an expression of viscosity relating to the time it takes for the volume of fluid to flow through that oriface.

Regards David

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Having consulted a book or two I can confirm John's thoughts. The Scale is Redwood 1 at 100 degrees F. In 1938 "...so-called diesel fuels had viscosities in the range 40-100 secs and Gas Oils were 35-45 seconds....". Source - Shell Petroleum Handbook. ttfn Roland

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AFAIK its the Redwood measurement.

Regards

Philip T-E

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In message , Peter Scales writes

Many thanks to all who answered - Redwood seems to be the consensus.

Regards

Pete

• posted

• posted

|The Society of Automotive Engineers (S.A.E.) scale is apparently the time it |takes for a steel sphere to fall a given distance within the sample fluid. |The units are apparently "pascal /seconds" and according to |"Etherington&Roberts" the value can vary 2% per degree C.!

I think you mean pascal seconds. (pascal/seconds indicates pascals divided by seconds, pascal seconds is pascals multiplied by seconds). The unit of dynamic viscosity is pascal seconds.

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