The main components of automotive LPG are propane and butane as well their certain homologous series.
Octane number is one of the main quality indicators of automotive LPG. Though it shall be 89 at least, most usually it is 90 or above for Motor Octane Number (MON).
Limitations are also applied on the content of unsaturated hydrocarbons with two double bonds, i.e. hydrocarbons tending to polymerize and form resinous compounds. The limit value for such compounds is not more than 0.5 mole percent dienic hydrocarbons.
Volume of sulfur compounds after odoration is also subject to limitation. Since LPG is an odorless gas, mercaptans are added as the special odorant so that any leaks can be easily detected. Mercaptans, according to their chemical composition, are the analogue of alcohols and contain a carbon-bonded sulfhydryl (R–SH) group. Even the smallest content of such substances, due to their strong odor, are easily detectable by the human nose; any presence of "gas" smell in a car shows the leakage of its gas system indicating to unsafe operation of the vehicle.
Automotive LPG, the same as gasolines, is also subject to determination of its corrosion aggressiveness, i.e. identification of the corrosion aggressiveness level for the sulfur compounds in gas. To determine corrosion aggressiveness a standard test is used which involves immersion of a copper strip in the product at 40 °C for one hour. Visual appearance and color changes of the strip give an indication of the corrosion activity.
Gauge vapor pressure is also limited to reduce hazards at the time of storage and during transportation. LPG is characterized by the high expansion coefficient, and is converted to liquid phase at the pressure of 16 atm; consequently, the higher the gauge pressure, the stricter are the requirements for the tanks and cylinders containing LPG.
It is this indicator which makes difference between the summer and winter grades of LPG. All grades of automotive LPG are subject to the gauge vapor pressure limitations not exceeding 1550 kPa at 40 °C. Winter grades of LPG are subject to limitation of minimum pressure being at least 150 kPa at max. temperature of minus 10 °C. This ensures the possibility of starting the engine in winter season. The referred indicator is guaranteed by ensuring the required propane content in gas mixture.
Density, like for all products, is not limited but determined at 15 °C.
Currently ORLEN Lietuva produces:
Automotive LPG (winter grade);
Automotive LPG (summer grade);
Household and commercial liquefied hydrocarbon gas;
Other LPG (propane/propylene fraction).