ASTM D4175 Terminology Relating to Petroleum, Petroleum Products, and Lubricants
T - in electromagnetics, symbol for transmittance.
takeoff power, n - for octane rating, normal or maximum rated power with the engine speed at maximum rated.
takeoff rate, n - the rate of product takeoff from the reflux divider expressed in millilitres per hour.
takeoff rate, n - in column distillation, the volume of product withdrawn from the reflux divider over a specified period.
tar, n - a brown or black, bituminous, liquid or semi-solid comprised primarily of bitumens condensed in the processing of coal, petroleum, oil-shale, wood, or other organic materials.
tar, n - a sticky, viscous, brown or black, bituminous material obtained from the destructive distillation of coal or other organic substances.

DISCUSSION - Although tar can be made from other organic substances, its normal source is bituminous coal. Therefore, its use in referring to petroleum products is discouraged except as a descriptive term.

target octane number, n - the research or motor octane number quality desired for a specific product.
taxa, pl., n - the units of classification of organisms, based on their relative similarities.

DISCUSSION - Each taxonomic unit (group of organisms with greatest number of similarities) is assigned, beginning with the most inclusive to kingdom, division, class, order, family, genus, and species. Bacteria and fungi are often further classified by strain and biovariation.

TDC, adj - top dead center

DISCUSSION - It is used with the degree symbol to indicate the angular position of the crankshaft from its position at the point of uppermost travel of the piston in the cylinder.

TEL - abbreviation for tetraethyllead (a gasoline antiknock agent).
temperature lag, n - the offset between the temperature reading obtained by a temperature sensing device and the true temperature at that time.
temperature measurement device, n - a thermometer, as described in 6.3.1, or a temperature sensor, as described in 6.3.2.
temperature reading, n - the temperature obtained by a temperature measuring device or system that is equal to the thermometer reading described in 3.1.19.
corrected temperature reading, n - the temperature reading, as described in 3.1.18, corrected for barometric pressure.
tensile strength, n - a property of solid material that indicates its ability to withstand a uniaxial tensile load.
terrestrial (or soil) environment, n - the aerobic environmental compartment which is found in and on natural soils.
test oil, n - any oil subjected to evaluation in an established procedure.

DISCUSSION - It can be any oil selected by the laboratory conducting the test. It could be an experimental product or a commercially available oil. Often, it is an oil that is a candidate for approval against engine oil specifications (such as manufacturers' or military specifications, and so forth).

test parameter, n - a specified component, property, or condition of a test procedure.

DISCUSSION - Examples of components are fuel, lubricant, reagent, cleaner, and sealer; of properties are density, temperature, humidity, pressure, and viscosity; and of conditions are flow rate, time, speed, volume, length, and power.

test procedure, n - one where test parameters, apparatus, apparatus preparation, and measurements are principal items specified.
test sample, n - a portion of the product taken at the place where the product is exchanged, that is, where the responsibility for the product quality passes from the supplier to the receiver. In the event that this is not possible, a suitable sampling location should be mutually agreed upon.
test sample - the weighed portion of the analysis sample actually used in a test.
test start, n - introduction of test oil into the engine.
TGF, n - top groove fill
theoretical carbon dioxide (ThCO2), n - the amount of CO2 which could theoretically be produced from the complete biological oxidation of all of the carbon in a test material.
theoretical CO2, n - the amount of CO2 which could in theory be produced from the complete oxidation of all the carbon in a material.
theoretical O2(oxygen), n - the amount of oxygen that is theoretically required to oxidize a material.

DISCUSSION - The appropriate abbreviation is ThO2.

theoretical O2, n - the amount of oxygen which would theoretically be required to completely oxidize a material.
theoretical plate, n - the section of a column required to achieve thermodynamic equilibrium between a liquid and its vapor.

DISCUSSION - The height equivalent to one theoretical plate (HETP) for packed columns is expressed in millimetres. In the case of real plate columns, the efficiency is expressed as the percentage of one theoretical plate that is achieved on one real plate.

thermal and oxidative stability, n - in lubricating oils used for manual transmissions and final drive axles, a lack of deterioration of the lubricating oil under high-temperature conditions that is observed as viscosity increase of the lubricating oil, insolubles formation in the lubricating oil, or deposit formation on the parts, or a combination thereof.
thermal stability, n - the resistance to permanent changes in properties caused solely by heat.
thermohydrometer, n - a glass hydrometer with a self-contained mercury thermometer.
thermometer reading (or thermometer result), n - the temperature of the saturated vapor measured in the neck of the flask below the vapor tube, as determined by the prescribed thermometer under the conditions of the test.
corrected thermometer reading, n - the thermometer reading, as described in 3.1.19, corrected for barometric pressure.
thickener, n - in lubricating grease, a substance composed of finely divided solid particles dispersed in a liquid lubricant to form the product's structure.

DISCUSSION - The thickener can be fibres (such as various metallic soaps) or plates or spheres (such as certain non-soap thickeners), which are insoluble or, at most, only very slightly soluble in the liquid lubricant. The general requirements are that the solid particles be extremely small, uniformly dispersed, and capable of forming a relatively stable, gel-like structure with the liquid lubricant.

thimble, n - in Soxhlet apparatus, a closed-end porous cylinder used to hold the material to be extracted, usually made of thick matted filter paper but sometimes made of ceramic.
thin film fluid lubricant, n - fluid lubricants consisting of a primary liquid with or without additives of lubricating powders and without binders or adhesives, which form a film on one or both surfaces to be lubricated and perform their function after application and after excess material has drained from the application area, and without additional material being supplied by either a continuous or intermittent method.
tight piston ring, n - in internal combustion engines, a piston ring that will not fall in its groove under its own weight when the piston, with the ring in a horizontal plane, is turned 90° (putting the ring in a vertical plane); by subsequent application of moderate finger pressure, the ring will be displaced.
time constant, n - in data acquisition, a value which represents a measure of the time response of a system. For a first order system responding to a step change input, it is the time required for the output to reach 63.2 % of its final value.
TIT, n - turbine inlet temperature
TLHC, n - top land heavy carbon
TNTC, n - too numerous to count
toluene insolubles, n - that portion of the pentane insolubles not soluble in toluene (methylbenzene).
toluene insolubles, n - in used oil analysis, the portion of pentane insolubles not soluble in toluene.
toluene standardization fuels, n - for knock testing, those volumetrically proportioned blends of two or more of the following: reference fuel grade toluene, n-heptane, and isooctane that have prescribed rating tolerances for O.N.ARV determined by round-robin testing under reproducibility conditions.
top size - the size of the smallest opening of one sieve of a series upon which is cumulatively retained a total of less than 5 % of the sample. This defined top size is not to be confused with the size of the largest particle in a lot.
total analyzer system response time, n - time interval between when a step change in property characteristic at the sample loop inlet and when the analyzer output indicates a value c corresponding to the 99.5 % of the subsequent change in analyzer results; the total analyzer system response time is the sum of the sample loop lag time, the same conditioning loop lag time, and the total analyzer response time.
total fluid constituent, n - in lubricating grease analysis, the n-hexane-soluble material extracted from the lubricating grease sample.

DISCUSSION - Typical materials include petroleum oil, non-petroleum fluid, soluble fats, and soluble additives.

total glycerin, n - is the sum of free and bonded glycerin.
total glycerin, n - the sum of the free glycerin and the glycerin portion of any unreacted or partially reacted oil or fat.
total n-hexane-insoluble material, n - in lubricating grease analysis, that portion of grease (excluding free alkali) that is essentially insoluble in n-hexane.

DISCUSSION - Typical materials include thickeners, fillers, inorganic salts, asphaltenes or any combinations of these (also includes insoluble materials found in the analysis of contaminated grease). Free alkali content is generally insignificant.

total sum of squares (TSS), n - a statistic used to quantify the information content from the inter-laboratory study in terms of total variation of sample means relative to the standard error of each sample mean.
toxicity, n - the propensity of a test material to produce adverse behavioral, biochemical, or physiological effects in a living organism.
traceability, n - property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties.
transmittance, n - of light, the fraction of the incident light of a given wavelength that is not reflected or absorbed, but passes through a substance.
transmittance, T, n - the fraction of radiant energy entering a substance that reaches its further boundary.
transmittance, T, n - the molecular property of a substance that determines its transportability of radiant power, expressed by:
T = P/Po
where:
P = the radiant power passing through the sample, and
Po = the radiant power incident upon the sample.

trap, n - a device utilized to selectively retain specific portions (individual or groups of hydrocarbons or oxygenates) of the test sample and to release the retained components by increasing the trap temperature.
Tristimulus Values, n - the amounts of three specified stimuli required to match a color.

DISCUSSION - In the CIE system, they are assigned the symbols X, Y, and Z.

true value, µ, n - in statistics, the value towards which the average of single results obtained by N laboratories tends, when N becomes very large.
true value (µ), n - for practical purposes, the value towards which the average of single results obtained by N laboratories using the same standard test method tends, when N becomes very large. Consequently, this definition of true value is associated with the particular test method employed.
TSA, n - tryptone soy agar
turbocharged/supercharged aircraft engine, n - aircraft piston engine that breathes with forced means from either turbochargers or superchargers.
Type I mineral oils, n - oils for steam and gas turbine lubricating systems where the machinery does not require lubricants with enhanced load carrying capacity.

DISCUSSION - Type I oils usually are available in ISO VG 32, 46, 68 and 100 (see Classification D2422). Such oils normally contain rust and oxidation inhibitors in addition to other additives as required to meet the specified performance characteristic. Type I oils are generally satisfactory for turbine sets where bearing temperatures do not exceed 110°C.

Type II mineral oils, n - oils for steam and gas turbine lubricating systems where the machinery requires enhanced load carrying capacity.

DISCUSSION - Type II oils usually are available in ISO VG 32, 46, 68, 100, and 150. These oils are similar to Type I but contain additional anti-wear additives for use in turbines equipped with a gearbox. Oils ISO VG 68 and above have been used in marine, hydro, or water turbines.

Type III mineral oils, n - oils for heavy duty gas or combined cycle turbine lubricating systems where the lubricant shall withstand higher temperatures and exhibit higher thermal stability than Type I mineral oils.

DISCUSSION - Type III oils usually are available in ISO VG 32 and 46. Such oils are normally comprised of a highly refined mineral base oil with suitable rust and oxidation inhibitors in addition to other additives as needed to meet specified performance characteristics. Type III oils are formulated for use in turbine sets where bearing temperatures may exceed 110°C. The turbine lubrication systems using Type III oils may be equipped with a gearbox that may require the selection of oils that contain additional anti-wear additives to impart the specified load carrying capacity.