– C –
Carbon Residue – The residue remaining after the evaporation of a sample of mineral oil under specified conditions, i.e., Ramsbottom and Conradson.
Centipoise (cP.) – A unit of absolute viscosity. 1 centipoise = 0.1 poise.
Centistoke (cSt.) – A standard unit of kinematic viscosity = 0.10 stoke
Cetane Number – A number that expresses the ignition quality fo diesel fuel and equal to the percentage by volume of cetane (C16H34) in a blend with methyl naphthalene, which blend has the same ignition performance to the test fuel.
Channel Point – Lowest safe temperature that a gear lubricant can be used.
Circulating Lubrication – A system of lubrication in which the lubricant, after having passed through a bearing or group of bearings, is re-circulated by means of a pump.
Cleveland Open Cup – See Flash Point, Fire Point
Coefficient of Friction – The ratio of the friction force between two bodies to the normal, or perpendicular, force between them.
Compounded Oil – A petroleum oil to which has been added other chemical substances.
Consistency – A term used synonymously with the term Penetration Number of a grease.
Corrosion – The attrition or wearing away of a substance by acid or electrochemical action.
Cup Grease – An early term for a calcium or lime base grease, practically obsolete now but meant originally to designate a degree of quality suitable for grease cup application.
Cutting Fluid or Oil – Any fluid applied to a cutting tool to assist in the cutting operation by cooling, lubricating or other means.