Disclosed are solvency enhancer compositions, for example, as additives to lubricating oils and as formulated in lubricating oil compositions and associated methods of preparation and use thereof. The compositions and methods can dissolve at least one of oxidation products and other organic polar compounds, due to lubricant degradation, formed and suspended in oil compositions including adding an effective amount of a solvency enhancer to the oils, wherein the solvency enhancer includes Guerbet alcohols. Further described are methods for dissolving organic deposits in an oil system including adding an effective amount of a solvency enhancer to the oil system, wherein the solvency enhancer includes Guerbet alcohols. Also provided are methods for preventing sludge and varnish formation in in-service oils including adding an effective amount of a solvency enhancer to the oils, wherein the solvency enhancer includes Guerbet alcohols.

Disclosed is a method of treating a used hydrocarbon lubricant of ISO Viscosity Grade 46 or higher comprising oxidation products that adversely affect lubricant performance. The hydrocarbon lubricant has a Group II hydrocarbon oil or Group III hydrocarbon oil, optionally one or more lubricant additives, and an amount of varnish. The hydrocarbon lubricant is free of zinc-containing additives. The method comprises adding to the used hydrocarbon lubricant from about 2 percent by weight to about 20 percent by weight of a polyhydroxy polypropylene oxide homopolymer that has a hydroxyl number of from about 12 mg KOH/g to about 58 mg KOH/g as measured according to ASTM D4274.

A method for re-refining used oils comprises contacting feedstock comprising purified used oil with extraction solvent to perform continuous liquid-liquid solvent extraction, to produce an extract stream comprising the extraction solvent and an extract dissolved in the extraction solvent. The feedstock and the extraction solvent are agitated by a variable speed agitator during the solvent extraction at a selected agitation speed. The extract is separated from the extraction solvent and subjected to a continuous flow liquid phase hydrogenation treatment to produce an oil product. A system for performing the method includes a purification unit for purifying the used oil; an extraction column for extracting the extract from the feedstock; and a continuous flow liquid phase hydrogenation unit. The extraction column comprises an agitator configured to agitate the feedstock and the extraction solvent flowing through the extraction column at a variable agitation speed.

A method for re-refining used oils comprises contacting feedstock comprising purified used oil with extraction solvent to perform continuous liquid-liquid solvent extraction, to produce an extract stream comprising the extraction solvent and an extract dissolved in the extraction solvent. The feedstock and the extraction solvent are agitated by a variable speed agitator during the solvent extraction at a selected agitation speed. The extract is separated from the extraction solvent and subjected to a continuous flow liquid phase hydrogenation treatment to produce an oil product. A system for performing the method includes a purification unit for purifying the used oil; an extraction column for extracting the extract from the feedstock; and a continuous flow liquid phase hydrogenation unit. The extraction column comprises an agitator configured to agitate the feedstock and the extraction solvent flowing through the extraction column at a variable agitation speed.

A process includes continuous steps and batch steps for recycling waste oil, fuel or antifreeze. The continuous steps include determining the volume of waste; pumping waste toward a distillation vessel; mixing waste with heated waste, and while flowing the waste into the distillation vessel performing steps of: maintaining a vacuum; heating the waste; returning a first portion of heated waste to the distillation vessel and a second-portion to mix with the waste feed; sending gaseous vapors to a condenser; returning some condensed liquid to the distillation vessel; and delivering condensed liquid as a product. The batch steps include: stopping waste flow into the distillation vessel; reducing pressure; heating the waste; returning the heated waste to the distillation vessel; condensing gaseous vapors; returning some condensed effluent to the distillation vessel; delivering some condensed effluent as a first product; and delivering heated waste as a second product.

A process includes continuous steps and batch steps for recycling waste oil, fuel or antifreeze. The continuous steps include determining the volume of waste; pumping waste toward a distillation vessel; mixing waste with heated waste, and while flowing the waste into the distillation vessel performing steps of: maintaining a vacuum; heating the waste; returning a first portion of heated waste to the distillation vessel and a second-portion to mix with the waste feed; sending gaseous vapors to a condenser; returning some condensed liquid to the distillation vessel; and delivering condensed liquid as a product. The batch steps include: stopping waste flow into the distillation vessel; reducing pressure; heating the waste; returning the heated waste to the distillation vessel; condensing gaseous vapors; returning some condensed effluent to the distillation vessel; delivering some condensed effluent as a first product; and delivering heated waste as a second product.

A process includes continuous steps and batch steps for recycling waste oil, fuel or antifreeze. The continuous steps include determining the volume of waste; pumping waste toward a distillation vessel; mixing waste with heated waste, and while flowing the waste into the distillation vessel performing steps of: maintaining a vacuum; heating the waste; returning a first portion of heated waste to the distillation vessel and a second-portion to mix with the waste feed; sending gaseous vapors to a condenser; returning some condensed liquid to the distillation vessel; and delivering condensed liquid as a product. The batch steps include: stopping waste flow into the distillation vessel; reducing pressure; heating the waste; returning the heated waste to the distillation vessel; condensing gaseous vapors; returning some condensed effluent to the distillation vessel; delivering some condensed effluent as a first product; and delivering heated waste as a second product.

A process includes continuous steps and batch steps for recycling waste oil, fuel or antifreeze. The continuous steps include determining the volume of waste; pumping waste toward a distillation vessel; mixing waste with heated waste, and while flowing the waste into the distillation vessel performing steps of: maintaining a vacuum; heating the waste; returning a first portion of heated waste to the distillation vessel and a second-portion to mix with the waste feed; sending gaseous vapors to a condenser; returning some condensed liquid to the distillation vessel; and delivering condensed liquid as a product. The batch steps include: stopping waste flow into the distillation vessel; reducing pressure; heating the waste; returning the heated waste to the distillation vessel; condensing gaseous vapors; returning some condensed effluent to the distillation vessel; delivering some condensed effluent as a first product; and delivering heated waste as a second product.