In Reply to: Re: The Hydraulic Oil Story posted by 36 coupe on December 27, 2013 at 18:57:52:
Viscosity is a physical property that we measure using a simple device called a viscometer and it is EXACTLY the same for conventioanl gear oil as it is for UTF.
I did not compare UTF to SAE 90 - I compared it to SAE 80 which is the viscosity Ford recommended for year round use in the NAA and Hundred series hydraulic systems. SAE 90 is a heavier oil and has a viscosity of 12.5 to 18.4 cSt @ 100C. It works better in your slap worn out 60 year old vane pump. UTF has the viscosity that Ford recommended in 1955 and which Vickers currently recommends for their vane pumps and works fine in pumps that are not slap worn out.
100C is the boiling point of water (212F) and is the test temperature that the SAE/API uses to classify the viscosity of gear and motor oils.
TOH
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