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Old 26 Apr 2008, 04:25 PM   #1 (permalink)
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Interesting Oil Facts #2

At which temperature does an oil flow better?

There is no temperature where oil suddenly starts to flow better.

A 10W/40 for example will flow between -25C and 100C or more, but there is some difference in the rate of flow! (True viscosity at -25C is about 7000 Centistoke(cSt) units, dropping to 14 at 100C. ‘Viscosity’ is really just another name for ‘rate of flow’.)

The correct question is at what (sump) temperature is an oil at a viscosity that suits a modern high-RPM engine? Present day designs are happy on an oil viscosity of 10 to 15 cSt. (But many are OK on less than 10.) 30cSt is too high at high RPM. It can lead to foaming, air entrainment and cavitation.

Temp. for 30cSt (DegC)..........Temp. for 15cSt ............Temp. for 10cSt

5W/40.........71.............................90...... ...........................117

10W/40.......70.............................99........ .........................118

10W/50.......80............................109........ ........................130

10W/60.......89............................119........ ........................142


As you will see from the above table a 5W/40 or a 10W/40 is perfectly adequate for all engines except those that run unusually high temperatures (120degC plus)

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The Opie Oils Team
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Old 26 Apr 2008, 09:24 PM   #2 (permalink)
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Good Thread Oilman, very interesting!!!!
One question 4 U.
When you refer to temperature, it is the external temperature of the air, or the temperature inside the engine?
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Old 26 Apr 2008, 09:32 PM   #3 (permalink)
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I refer to sump temperature

Cheers
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Old 02 Jun 2008, 02:35 PM   #4 (permalink)
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what oil would you recommed for an Impreza?

A friend of mine recommended silkolene pro s 5w-40
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Old 02 Jun 2008, 04:30 PM   #5 (permalink)
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WHat year is it? And is it modded at all?

Cheers

Guy.
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Old 15 Jun 2008, 09:53 PM   #6 (permalink)
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Very interesting, Oilman.

I thought that I had come across pretty much all units of measurement (including the Twip and the Hogshead), but the centistoke is a new one on me! It's amazing what you can find out when you Wiki something like this.

Howard
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Old 19 Jun 2008, 01:24 PM   #7 (permalink)
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of what would be best for running between 80degrees c and 90 degrees c?
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Old 19 Jun 2008, 02:11 PM   #8 (permalink)
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5w-40 or 10w-50 for a bot of over kill.

Cheers

Guy.
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Old 22 Jun 2008, 10:32 PM   #9 (permalink)
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Quote:
Originally Posted by oilman View Post
5w-40 or 10w-50 for a bot of over kill.

Cheers

Guy.

coolio, im running silk pro s whic i think is qabout that
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Old 23 Jun 2008, 08:34 AM   #10 (permalink)
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Cant go wrong with the Silkolene.
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