Diesel versus Petrol: What’s the advantages and disadvantages?

We occasionally get asked by our customers whether or not they should put a diesel engine in their vessel, or a petrol engine. As with everything else in life, there is no single “right or wrong” answer. We manufacture both types of engines, so we are truly non-biased in our opinion. The answer is, “It depends.”

Ask yourself these questions:

What is the purpose of the vessel?

How will the vessel be used?

What are the emissions regulations in my area?

What is my budget?

These all have an impact. So, to make things easier to break down, we will use diesel as a starting point, listing advantages and disadvantages versus petrol.

Advantages

  1. More efficient combustion versus petrol. Diesel engines have a much higher output of torque than petrol engines. Given the same horsepower on two engines (see below), the diesel will provide more work for the fuel spent.
  2. Much longer life cycle that petrol engines. As much as three or four times longer. Petrol engines work “harder” to produce the same power, and are more complex, thus needing more frequent maintenance.
  3. Diesel is cheaper than petrol (At least in most of the world).
  4. Much lower fuel consumption.
  5. Petrol has a greater risk of explosion and fire. Requires greater ventilation.
  6. Diesel engines produce much less heat, and are cooled more efficiently. Petrol engines can require substantial cooling systems at greater cost.

 

Disadvantages

  1. Diesel engines are usually more expensive than petrol engines, often up to twice the price.
  2. Diesel engines produce more smoke with dirty fuel (Though ULSDF required in Europe and the USA is actually cleaner than petrol).
  3. Diesel fuel breaks down rapidly. If engines will sit for long periods of time, the fuel will need to be stabilized or drained.

The pictures below illustrate two MD engines’ power and torque curves, showing a big difference in torque, but producing the same horsepower.

petrol 6-2

MD VGT 400 diesel power and torque curves.

MD VGT 400 diesel power and torque curves.