Abstract: The thermal stability of jet fuel sweetened by oxidation is improved by washing the sweetened fuel with strong aqueous caustic.

Abstract: A process is disclosed for the preparation of a lubricating base oil with a high viscosity index and a low pour point by catalytic dewaxing, which process comprises contacting at dewaxing conditions a feedstock containing at least part of the hydrocrackate of a wax-containing mineral oil fraction, which feedstock has a kinematic viscosity at 100.degree. C. of, at most, 10 mm.sup.2 /s, with a dewaxing catalyst. The invention further provides a lubricating mineral base oil comprising hydrocarbons with a boiling point of at least 250.degree. C., and having a viscosity index of at least 125 and a pour point of at most -25.degree. C.