Why Do Diesel Generators Lose Efficiency Over Time?

It is assumed that a diesel generator would generate power efficiently within a number of years. Nonetheless, constant use would see the reduction in the efficiency levels. The generator that once was fuel-efficient and efficient in terms of generating energy becomes inefficient in terms of burning fuel and producing power.

Does it mean that you should replace your generator? Of course not! This level of inefficiency is usually due to certain things that can be addressed.

1. Engine Wear and Tear

Engine is the backbone of any diesel generator. Over time, some of the parts of the engine like piston rings, cylinder liners, valves, and bearings start wearing off.

As the wear happens, engine's efficiency starts reducing, which increases the fuel usage and exhaust emissions.

Inspection and maintenance of the engine will ensure that the components of the engine work in good condition.

2. Poor Quality and Contaminated Fuel

Quality of the fuel affects the performance of the generator to a great extent. Poor quality of the fuel, presence of water and contaminants in the fuel can have negative impact on the working of the generator.

Clogged fuel filters or dirty injectors may cause insufficient fuel flow to the engine.

Proper fuel quality can help to solve the above problems.

3. Clogged Air Filters

The proper function of a diesel engine requires an adequate flow of clean air for successful combustion. The air filter being clogged by dust and dirt restricts the flow of air.

This will result in the engine not receiving enough air and the process of combustion will be affected negatively causing under-performance and fuel inefficiency.

Inspecting and changing the air filters as advised is an easy maintenance procedure.

4. Issues with Fuel Injectors

Fuel injectors spray diesel into the engine in the right pressure and time. As the fuel injectors age, they get dirty, worn out and even damaged.

If the fuel injectors do not function properly, the combustion process will be affected negatively and this will cause more smoke and higher fuel consumption.

5. Operation Below the Required Load Level

All diesel engines are designed to work under certain load levels. If the machine works constantly below its load level, it becomes less efficient, and carbon deposits can occur inside the engine.

Operating above the capacity of the engine is yet another aspect that affects the engine and the alternator of the generator.

It is essential to choose the right size of the generator and the working load to have an optimal performance of the generator.

6. Inadequate Engine Cooling and Lubrication

The adequate cooling and lubricating systems are necessary to make the generator highly efficient. Absence of coolant, blockage of the radiator, and inadequate air flow can increase the engine's temperature.

Inadequate lubricant will add friction to the engine's operation.

The right maintenance as recommended by the manufacturer, in particular, oil changes and coolant system cleaning, must be done.

7. Absence of Preventive Maintenance

Failure to have proper maintenance is one of the most common causes of generator inefficiency.

Signs such as strange sounds, too much smoke, over heating, oil leakage, and high fuel consumption should not be ignored since small issues can become serious problems.

Preventive maintenance will reveal possible problems before they cause serious damage to the generator.


Inefficiency in diesel generators can be caused by many factors such as wear and tear of the engine, poor quality of fuel, clogging of filters, injector failure, improper loading, cooling or lubrication, and inadequate maintenance.

Proper servicing, correct loading, and replacement of worn parts are important in ensuring that a generator remains efficient in fuel use and performance. Professional examination is advised in case there is high consumption of fuel and reduction in power output of a generator.