Soot control for diesel engine lubricants

Abstract

The present invention is directed to a method for controlling soot induced viscosity increase in diesel engines, by using as the diesel engine lubricant an oil formulation comprising a base oil containing about 10 to 80 wt % GTL base stock and / or base oil and / or hydrodewaxed or hydroisomerized / catalytic (or solvent) dewaxed base stock and / or base oil in combination with 20 to 90 wt % conventional Group I petroleum derived base oil, said base oil being further combined with a polymeric viscosity modifier, and to the lubricating oil which effects such control over soot induced viscosity increase.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 60 / 788,213 filed Mar. 31, 2006.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to diesel engine lubricating oils and to the control of soot induced viscosity increase of the lubricating used in such engines.[0004]2. Description of the Related Art[0005]Internal combustion engines function by the combustion of fuels which in turn generate the power needed to propel vehicles. In the case of a diesel engine, the fuel is a diesel fuel and the combustion thereof generally results in emissions from the exhausts of such vehicles which comprise three main components. These are: soot and particulate matter, carbon monoxide and nitrogen oxides (the latter will hereafter be abbreviated as NOx for convenience). To alleviate environmental concerns, research is ongoing to reduce the levels of these emissions. NOx emission can be reduced ...

AI Technical Summary

Problems solved by technology

In the case of a diesel engine, the fuel is a diesel fuel and the combustion thereof generally results in emissions from the exhausts of such vehicles which comprise three main components.

However, this retarded combustion has the disadvantage that it causes more soot to accumulate in the engine lubricant partly due to incomplete combustion of the fuel because of the lower combustion temperature, and partly due to increased soot deposition on the cylinder wall which is drawn down into the lubricant with the downward stroke of the piston.

The presence of soot in the lubricant has the adverse affects of causing viscosity increase and accelerated wear.

However, the higher temperatures whilst mitigating the formation of soot also result in the formation of increased amounts of NOx.

If, however, the engine temperature is lowered, incomplete combustion ensues and whilst this reduces the amount of NOx formed in the emissions, it also substantially increases the amount of soot generated.

As the soot builds up in the lubricant, the latter becomes more and more viscous and upon reaching a critical value can cause gelation of the lubricant and may eventually cause seizure of the engine.

Consequently, such wax isomerate base oils would be expected to have low solvency and poor additive solubility performance.

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