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
------------- Use the code BAVBOARD and get 10% Club Discount email: sales@opieoils.co.uk Phone: 01209 202944
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