This is often caused by the generator not being sized correctly in the first place. It is critical that a generator is sized correctly especially when the load is constantly the same, to prevent glazing and also to be fuel efficient.
Operating diesel engines at light loads for extended periods of time can cause glazing to the cylinder bores. This occurs because poor combustion can lead to soot formation and unburnt fuel residue which clogs & gums up piston rings which causes the piston rings to not seal as well. Glazing of the cylinder bores occurs when hot combustion gases blow past the now poorly sealing piston rings and creates a glaze on the cylinder bore & increased oil consumption. This can lead to oil entering the exhaust, heavy carbon build up on: pistons, piston rings & ring grooves, valves & valve guides, cylinder head ports & exhaust pipes, and turbocharger seals on turbo charged engines.
If this is caught in early stages, increasing the load on the generator can burn the residues away, however if it is left unchecked, the engine can be damaged to point where it has to be rebuilt or replaced.
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