A method of lubricating a marine diesel 2-stroke engine comprising: (1) monitoring performance characteristics of said engine; (2) selecting a lubricating composition to modify the performance characteristics of the engine, wherein the lubricating composition is prepared by in-situ controlled blending of at least two different fluids, said fluids comprising: (i) a first fluid comprising an additive package with one or more overbased detergents, and optionally other performance additives; (ii) a second fluid comprising an additive package with one or more neutral detergents or overbased detergents, and optionally other performance additives, with the proviso that the first fluid has a ratio of Σ(wt % of overbased detergents)/Σ(wt % of all additives in the fluid) greater than the second fluid; and (iii) a third fluid comprising an oil of lubricating viscosity; and (3) supplying the lubricating composition of step (2) to the engine, with the proviso that the lubricating composition comprises at least one of the first fluid or the second fluid.