Interesting Oil Facts #2
26 April 2008 | 05:48 PM
#1
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)
Cheers
The Opie Oils Team
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)
Cheers
The Opie Oils Team
if so i'm in trouble as i wait to see 80odd before pressing on a bit
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27 April 2008 | 08:14 PM
#8
Scooby Senior
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From: Slowly rebuilding the kit of bits into a car...
I don't think a road car is going to suffer from centistoke-itis myself...
I expect to blow mine up in the next two years, if the clutch lasts that long
LOL
DunxC
I expect to blow mine up in the next two years, if the clutch lasts that long
LOL
DunxC
27 April 2008 | 08:35 PM
#9
80degC is an acceptable temp for pushing the loud pedal, I would not do it at 40degC though.
If your car never sees 80degC then a 5w-40 or 10w-40 would be better than a 10w-50 or 15w-50
Cheers
If your car never sees 80degC then a 5w-40 or 10w-40 would be better than a 10w-50 or 15w-50
Cheers
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