Cummins 4BT โ€“ Lubricating Oil Dilution

Caution: Diluted oil can cause severe engine damage.
Check the condition of the lubricating oil.
โ€ข Thin, black lubricating oil is an indication of fuel in the oil.
โ€ข Milky discoloration is an indication of coolant in the lubricating oil.

Coolant in the oil can be caused by:
โ€ข Expansion plugs leaking.
โ€ข Lubricating oil cooler element leaking.
โ€ข Damaged cylinder head or gasket.
โ€ข Cracked engine block.
โ€ข Casting porosity