ASTM D4175 Terminology Relating to Petroleum, Petroleum Products, and Lubricants
obligate aerobe, n - microorganism with an absolute requirement for atmospheric oxygen in order to function.
DISCUSSION - Obligate aerobes may survive periods in anoxic environments but will remain dormant until sufficient oxygen is present to support their activity.
obligate anaerobe, n - microrganism that cannot function when atmospheric oxygen is present.
DISCUSSION - Obligate anaerobes may survive periods in oxic environments but remain dormant until conditions become anoxic.
observed dropping point, n - the value noted on the thermometer monitoring the internal temperature of the grease test cup when the first drop of material falls from the test cup and reaches the bottom of the test tube.
octane number, n - for spark ignition engine fuel, any one of several numerical indicators of resistance to knock obtained by comparison with reference fuels in standardized engine or vehicle tests.
DISCUSSION - In the context of this test method, octane number is understood to mean the numerical indicator of knock obtained by comparison with primary reference fuels in a standardized CFR engine operating under conditions specified in either the Research, Test Method D2699 or Motor, Test Method D2700, standards.
research octane number, n - for spark-ignition engine fuel, the numerical rating of knock resistance obtained by comparison of its knock intensity with that of primary reference fuel blends when both are tested in a standardized CFR engine operating under the conditions specified in this test method.
odor, n - of a wax, the numerical rating corresponding to the odor scale description that best fits the sample being tested.
oil separation, n - the appearance of a liquid fraction from an otherwise homogeneous lubricating composition.
open cell, n - in carbon and graphite technology, a cell that is not totally enclosed in its walls and hence interconnected with other cells. An open-cell foam is a foam consisting predominantly of open or connected cells.
operationally valid standard test, n - in automotive lubricant testing, a standard test that meets operational validity requirements, where specified.
DISCUSSION - Operational validity is determined after a test is completed. Requirements can include (1) mid-limit ranges for the average values of primary and secondary parameters that are narrower than the specified control ranges, (2) allowable deviations for primary and secondary parameters from the specified control ranges, (3) downtime limitations, and (4) special parameter limitations.
operator, n - a person who normally and regularly carries out a particular test.
orientation (of a crystal), n - the angular position of a crystal described by the angles which certain crystallographic axes make with the frame of reference.
orientation (of a grain), n - the angular position of a grain described by the angles which a defined set of axes of the grain make with the stated frame of reference. Generally used to characterize the axis of the grain that has the largest physical extent, for example, in a grain of needle coke.
orientation (of an object), n - the angular position of an object described by the angles which a defined set of axes or surfaces of the object make with the frame of reference.
Ostwald coefficient, n - the solubility of a gas, expressed as the volume of gas dissolved per volume of liquid when both are in equilibrium at the specified partial pressure of gas and at the specified temperature.
out of specification data, n - in data acquisition, sampled value of a monitored test parameter that has deviated beyond the procedural limits.
outaging, n - practice of removing a portion of liquid contents from a conventional sampling cylinder after filling to provide expansion room.
outlier, n - a result far enough in magnitude from other results to be considered not a part of the set.
oxic, adj - an environment with a sufficient partial pressure of oxygen to support aerobic growth.
oxidation, n - of engine oil, the reaction of the oil with an electron acceptor, generally oxygen, which can produce deleterious acidic or resinous materials often manifested as sludge formation, varnish formation, viscosity increase, or corrosion, or a combination thereof.
oxidation, n - of engine oil, the reaction of the oil with an electron acceptor, generally oxygen, that can produce deleterious acidic components often manifested as sludge formation, varnish formation, viscosity increase, or corrosion, or combination thereof.
oxidation of carbon, n - the chemical combination of carbon with oxygen or oxygen-containing compounds.
oxidative combustion, n - process in which a sample undergoes combustion in an oxygen rich environment at temperatures greater than 650°C and compounds decompose to carbon dioxide, water, and elemental oxides.
oxygenate, n - an oxygen-containing, ashless, organic compound, such as an alcohol or ether, which may be used as a fuel or fuel supplement.
oxygenate, n - an oxygen-containing organic compound, which may be used as a fuel or fuel supplement, for example, various alcohols or ethers.
