Boat Diesel – Mixing oils

Engine lubricating oils are designed to be mixable with oils of a different standard. Engines cover a wide range of service conditions from low powered, lightly loaded applications to heavily loaded applications using high powered turbo engines. The specification of lubricating oils reflects the service conditions, for example the more taxing the service the higher the specification of oil required.

Naturally aspirated engines, particularly those operating in lightly loaded applications, may need a lower grade oil for running in, to bed in the bores and avoid bore polishing which can result in high lubricating oil consumption. Consult the manufacturer for recommendations when running in a new or reconditioned engine.

Where a high sulphur content fuel is used, the lubricating oil should be changed more frequently.

Oil companies can provide an oil analysis service which can determine wear rates and combustion efficiency.

In the writer’s experience it is difficult to buy anything but high grade car diesel lubricating oil at automobile filling stations and oil suppliers are always in large towns miles away from the coast or any marinas. If a long trip is planned take at least enough oil and spare filters for as many changes as you expect to make and avoid any anxiety caused by exceeding the recommended change interval or using oil that you are unsure of.

Waste oil and the oily water found in the bilges should never be disposed of in the sea or inland waterways. As well as damaging the environment, this is illegal and could result in a heavy fine. Most marinas offer disposal facilities, and these should be used.

Oil absorbing mats are now available which can be laid under the engine or in the bilge.

These will absorb oil/fuel and can be disposed of correctly ashore.

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