ASTM D4175 Terminology Relating to Petroleum, Petroleum Products, and Lubricants
debris, n - in internal combustion engines, solid contaminant materials unintentionally introduced into the engine or resulting from wear.

DISCUSSION - Examples include such things as gasket material, silicone sealer, towel threads, and metal particles.

debutanization, n - of crude petroleum, the removal of the light hydrocarbons up to and including n-butane, and retention of the heavier hydrocarbons.

DISCUSSION - In practice, a crude petroleum is regarded as debutanized if the light hydrocarbon cut collected in the cold trap contains more than 95 % of the C2 to C4 hydrocarbons and less than 5 % of the C5 hydrocarbons initially present in the sample.

decomposition, n - of a hydrocarbon, the pyrolysis or cracking of a molecule yielding smaller molecules with lower boiling points than the original molecule.

DISCUSSION - Characteristic indications of thermal decomposition are evolution of fumes and erratic temperature readings that usually decrease after any attempt is made to adjust the heat.

decomposition point, n - the corrected thermometer reading that coincides with the first indications of thermal decomposition of the liquid in the flask.

DISCUSSION - The decomposition point, as determined under the conditions of this test method, does not necessarily correspond to the decomposition temperature in other applications.

decomposition point, n - corrected thermometer reading that coincides with the first indications of the liquid in the specimen container.

DISCUSSION - Characteristic indications of thermal decomposition are evolution of fumes and erratic, typically decreasing, temperature readings that occur during the final stages of the distillation.

DISCUSSION - The decomposition point, as determined under the conditions of this test method, does not necessarily correspond to the decomposition temperature in other applications.

defect, n - of a manufactured carbon or graphite product, any irregularity in the chemistry, microstructure, or macrostructure.
defective, adj - having flaws or dimensional deviations greater than acceptable for the intended use.
degras (wool fat, wool grease, wool wax), n - a fat-like material comprised primarily of sterols, other higher alcohols, and fatty acids, obtained from the solvent extraction of sheep's wool.
degree of thickening (DT), n - the ratio of an oil's viscosity with an additive to that oil’s viscosity without the additive. A measure of the amount by which an additive increases the base fiuid viscosity.
degrees of freedom, n - the divisor used in the calculation of variance.

DISCUSSION - This definition applies strictly only in the simplest cases. Complete definitions are beyond the scope of this practice.

demulsibility, n - in petroleum products, the ability of a mixture of liquids (usually hydrocarbons and water) to separate into its components after the mixture has been vigorously agitated.
denaturants, n - natural gasoline, gasoline components, unleaded gasoline, or toxic or noxious materials added to fuel ethanol to make it unsuitable for beverage use but not unsuitable for automotive fuel use.
denatured fuel ethanol, n - fuel ethanol made unfit for beverage use by the addition of denaturants.
density, n - mass per unit volume at a specified temperature.
density - the weight in vacuo, (that is, the mass) of a unit volume of the material at any given temperature.
density, n - the mass per unit volume. In the SI, the unit of density is the kg/m3, but for practical use, a submultiple is more convenient. The g/cm3 is 10(-3) kg/m3 and is customarily used.
density, n - the mass of liquid per unit volume at 15°C and its saturation pressure with the standard unit of measurement being kilograms per cubic metre.

DISCUSSION - Other reference temperatures, such as 20°C may be used for some products or in some locations. Less preferred units of measurement; for example, kg/L or g/mL, are still in use.

depacifying, adj - the process of removing hydrogen ions (protons) from the cathodic surface of an electrolytic cell, thereby promoting continued electrolytic corrosion.

deplasticize, v - the process of breaking down polymers in plastics and similar materials, resulting in loss of the material's structural integrity.
detection limit, n - a stated limiting value that designates the lowest concentration that can be determined with confidence and that is specific to the analytical procedure used.
detection limit, n - the smallest concentration of an element that can be measured for specific analysis conditions and data collection periods.
determinability, n - a quantitative measure of the variability associated with the same operator in a given laboratory obtaining successive determined values using the same apparatus for a series of operations leading to a single result; it is defined as that difference between two such single determined values as would be exceeded in the long run in only one case in 20 in the normal and correct operation of the test method.

DISCUSSION - This definition implies that two determined values, obtained under determinability conditions, which differ by more than the determinability value should be considered suspect. If an operator obtains more than two determinations, then it would usually be satisfactory to check the most discordant determination against the mean of the remainder, using determinability as the critical difference.

determination, n - the process of carrying out the series of operations specified in the test method whereby a single value is obtained.
detonation meter, n - for knock testing, the signal conditioning instrumentation that accepts the electrical signal from the detonation pickup and provides an output signal for display.
detonation pickup, n - for knock testing, a magnetostrictive-type transducer that threads into the engine cylinder and is exposed to combustion chamber pressure to provide an electrical signal that is proportional to the rate-of-change of cylinder pressure.
developer, n - of an ASTM test method, the assigned ASTM group, working under the supervision of its governing subcommittee and main committee, that formats the test method in accordance with the Form and Style for ASTM Standards, and continually refines the test method.
developer, n - of a test procedure, an individual or organization that selects the test apparatus and operating conditions.
dial indicator reading, n - for the CFR engine, a numerical indication of cylinder height, in thousandths of an inch, indexed to a basic setting at a prescribed compression pressure when the engine is motored.
diesel fuel, n - middle petroleum distillate fuel.
diesel fuel, n - petroleum-based middle distillate fuel.
diesel fuel oil, n - any petroleum liquid suitable for the generation of power by combustion in compression ignition (diesel) engines.

DISCUSSION - Different grades are characterized primarily by viscosity ranges and by minimum cetane numbers.

diesel index, n - an approximation of the cetane number (the ignition performance) of diesel fuel, calculated from the density and the aniline point. (No longer widely used for distillate fuels but applicable to some blended distillate residual fuels (see also cetane index).)
diffuser, n - for gas, a device for dispersing gas into a fluid.

DISCUSSION - In this test method the diffuser may be made of either metallic or non-metallic materials.

diffuser, n - for gas, a device for dispersing gas into a liquid. (Test Method D892).

DISCUSSION - Although diffusers can be made of either metallic or non-metallic materials, in this test method the diffuser is sintered stainless steel.

digital counter reading, n - for the CFR engine, a numerical indication of cylinder height, indexed to a basic setting at a prescribed compression pressure when the engine is motored.
dilution factor, f, n - the proportion of solvent increase made to reduce the concentration and thus the absorbance of a solute, expressed by the ratio of the volume of the diluted solution to the volume of original solution containing the same quantity of solute as the diluted solution.
DIN - abbreviation for Deutsches Institut für Normung (the German Standards Body).
dispersant, n - in engine oil, an additive that reduces deposits on oil-wetted engine surfaces primarily through suspension of particles.
dispute, n - when there is a question as to product quality conformance to specification because a test value obtained falls outside the specification limit(s).
dissolved and free water - water may be present in the fuel as dissolved water or as "free" (undissolved) water, or both. The free water may be fresh or saline. Fresh water may enter the fuel from steam coils in storage tanks, from condensation out of moisture-laden air, or from leaking cooling coils. Saline water can enter the fuel during transportation in barges or tankers.
distillate, n - in the petroleum industry, an overhead or side stream liquid from a distillation process. (Synonym - petroleum distillate.)

DISCUSSION - Distillates can be produced either directly from crude oil (called straight-run distillates) or from distillation after processing crude oil by cracking, coking, hydrocracking, or other conversion processes. The term is often given a modifier, such as cracked distillate.

DISCUSSION - The term distillate is sometimes used to mean middle distillate. This practice is discouraged.

distillation pressure, n - the pressure measured as close as possible to the point where the vapor temperature is taken, normally at the top of the condenser.
distillation residue, n - that portion of the sample remaining after distillation using specified procedures.
distillation temperature, n - in column distillation, the temperature of the saturated vapor measured just above the top of the fractionating column. (Synonym - head temperature, vapor temperature.)
double-blind reference oil, n - a reference oil, the identity of which is unknown by either the submitting source or the test facility and is not known to be a reference oil by the test facility.

DISCUSSION - This is a coded reference oil that is supplied by an independent source to a second party, who applies their own coded designation to the oil (and if necessary, repackages it to preserve its anonymity), and submits it to a third party for testing.

double-blind test, n - a standard test performed on a double-blind reference oil.
drain and dry mode, n - the effect from being sprayed, dipped, or brushed with a fluid lubricant and the excess material draining from the surface leaving behind a thin film that remains wet and must act as a lubricant on its own, without benefit of recirculation or continuous supply.
drop melting point of petroleum wax, n - the temperature at which material becomes sufficiently fluid to drop from the thermometer used in making the determination under definite prescribed conditions.
dropping point, n - a numerical value assigned to a grease composition representing the corrected temperature at which the first drop of material falls from the test cup and reaches the bottom of the test tube.

DISCUSSION - In the normal and proper operation of this test method, the observed dropping point is corrected by adding to it a value representing one third of the difference between the oven block temperature and the observed dropping point temperature. This corrected value is recorded as the dropping point of the grease.

dry method, n - in vapor pressure methods, a specific empirical test method (D 4953) for measuring the vapor pressure of gasoline and other volatile products in which contact of the test specimen with water is not allowed.
dry point, n - in batch distillation, the temperature observed at the instant the last drop of liquid evaporates from the lowest point in the flask.
dry point, n - the corrected thermometer reading that is observed at the instant the last drop of liquid (exclusive of any drops or film of liquid on the side of the flask or on the temperature sensor), evaporates from the lowest point in the distillation flask.

DISCUSSION - The end point (final boiling point), rather than the dry point, is intended for general use. The dry point can be reported in connection with special purpose naphthas, such as those used in the paint industry. Also, it is substituted for the end point (final boiling point) whenever the sample is of such a nature that the precision of the end point (final boiling point) cannot consistently meet the requirements given in the precision section.

dry solid film lubricants, n - dry coatings consisting of lubricating powders in a solid matrix bonded to one or both surfaces to be lubricated.
dry vapor pressure equivalent (DVPE), n - value calculated by a defined correlation equation, that is expected to be comparable to the vapor pressure value obtained by Test Method D4953, Procedure A.
DT - in viscometry, abbreviation for degree of thickening.
dynamic, adj - in petroleum products - in petroleum product flash point test methods—the condition where the vapor above the test specimen and the test specimen are not in temperature equilibrium at the time that the ignition source is applied.

DISCUSSION - This is primarily caused by the heating of the test specimen at the constant prescribed rate with the vapor temperature lagging behind the test specimen temperature.

dynamic fuel level, n - for knock testing, test procedure in which the fuel-air ratio for maximum knock intensity for sample and reference fuels is determined using the falling level technique that changes carburetor fuel level from a high or rich mixture condition to a low or lean mixture condition, at a constant rate, causing knock intensity to rise to a maximum and then decrease, thus permitting observation of the maximum knockmeter reading.
dynamic hold-up, n - in column distillation, the quantity of liquid held up in the column under normal operating conditions.
dynamic hold-up, n - the quantity of liquid held up in the column under normal operating conditions.

DISCUSSION - It is expressed as a percentage of the packed volume for packed columns so that the data can be compared. For real plate columns, it is expressed in millilitres per plate. The data can only be compared with others of the same diameter because of different tray spacing. Data for packed columns cannot be compared with those of real plate columns except in absolute units of millilitres per theoretical plate (see Table 1). Dynamic hold-up increases with increasing distillation rate up to the flood point and varies from one kind of fractionator to another.

dynamic holdup, n - the amount of material present in the neck of the flask, in the sidearm of the flask, and in the condenser tube during the distillation.
dynamic holdup, n - amount of material present in the distillation column, and in the condenser during the distillation.
dynamic viscosity (η), n - the ratio between the applied shear stress and rate of shear of a liquid.

DISCUSSION - It is sometimes called the coefficient of dynamic viscosity or, simply, viscosity. Thus, dynamic viscosity is a measure of the resistance to flow or to deformation of a liquid under external shear forces.

DISCUSSION - The term dynamic viscosity can also be used in a different context to denote a frequency-dependent quantity in which shear stress and shear rate have a sinusoidal time dependence.