Diesel engines normally use a little more oil than petrol engines and the colour of new oil quickly becomes black. The dipstick indicates the level and condition of the oil. If the level goes up and the oil is discoloured – grey or white, for instance – that’s a sure sign it is contaminated with water. This may be due to failure of a gasket or seal in the engine and generally involves a major repair. Running with contaminated oil will result in bearing failures. In an emergency replace the oil, but keep the speed low.
If you regularly have to top up to maintain the correct level, refer to Chapter 5. Always keep enough oil on board for a complete oil change.
Oil changes should be made in line with the engine manufacturer’s recommendations – normally 100 or 200 hours or at the end of every season, whichever is sooner.