The present invention provides a method for determining the authenticity of a petroleum hydrocarbon allegedly comprising at least one specific chemical marker, as well as a method for determining adulteration of a petroleum hydrocarbon marked with at least one specific chemical marker. The methods claimed and described herein rely upon the use of specific chemical markers in combination with laser ionization at a wavelength of between about 300 nm and about 370 nm coupled with ion mobility spectrometry or with mass spectrometry.

Provided is a lubricating oil composition comprising a base oil (A) containing a polyalkylene glycol (A1) and a polyol ester (A2), a phosphorus-based rust inhibitor (B), and an antioxidant (C) containing an amine-based antioxidant (C1). The lubricating oil composition exhibits a strong effect for suppressing sludge sedimentation even when used for an extended period of time in a high-temperature environment, and has excellent demulsibility and rust preventive properties, and therefore, can be suitably used in turbomachinery, compressors, hydraulic equipment, and machine tools.

A method for improving viscosity control, while maintaining or improving deposit control and cleanliness, of a lubricating oil in an engine or other mechanical component lubricated with the lubricating oil by using as the lubricating oil a formulated oil. The formulated oil has a composition including a lubricating oil base stock as a major component, and at least one oligomeric or polymeric aminic antioxidant, as a minor component. The at least one oligomeric or polymeric aminic antioxidant is formed in situ from at least one monomeric aminic antioxidant during operation of the engine or other mechanical component. The at least one monomeric aminic antioxidant is present in an amount sufficient to form in situ the at least one oligomeric or polymeric aminic antioxidant during operation of the engine or other mechanical component.

Provided is a lubricating oil composition comprising a base oil (A) containing a polyalkylene glycol (A1) and a polyol ester (A2), a phosphorus-based rust inhibitor (B), and an antioxidant (C) containing an amine-based antioxidant (C1). The lubricating oil composition exhibits a strong effect for suppressing sludge sedimentation even when used for an extended period of time in a high-temperature environment, and has excellent demulsibility and rust preventive properties, and therefore, can be suitably used in turbomachinery, compressors, hydraulic equipment, and machine tools.