8 Pros and Cons of Common Rail Diesel Engines

Common rail diesel engines are the modern version of diesel engines. Most of the diesel-powered vehicles you see today will have common rail technology in it. If you’re unfamiliar with common rail, it is a term that defines the fuel injection system used for these engines.

Common rail uses a high-pressure rail to deliver fuel to each solenoid valve. This is opposed to the traditional direct fuel injection system of using low-pressure pump nozzles to deliver fuel while producing more emissions.

Related: Pros and Cons of the Duramax Diesel Engine

Top 5 Advantages of Common Rail Diesel Injection

The common rail diesel engine allows for better emission control and consumption of fuel and power. In other words, common rail diesel engines can deliver more power to the vehicle while consuming less fuel and producing fewer emissions.

For these reasons, it complies with government regulators who want to put a cap on the volume of carbon emissions produced by a vehicle. Here are five advantages of a common rail diesel vs direct injection.

1) Lower Emissions

black smoke from exhaust

One of the reasons that common rail diesel engines were invented by vehicle manufacturers was because the government created stricter regulations on carbon emissions. Remember when big diesel trucks used to release a lot of black smoke into the air?

You hardly see that anymore because the common rail diesel engine is designed to reduce those emissions. This is better for the environment whether you believe in global warming or not.

Related: How to Reduce Black Smoke in Diesel Engines

2) More Power

Studies have shown that vehicles with a common rail diesel engine will produce 25% more power than a traditional diesel engine. This means the overall performance of the diesel engine will be improved.

3) Less Noise

strange noise

Direct fuel injection systems were known for being noisy while driving. The common rail will reduce a lot of the noise that you might remember hearing. This makes it a more pleasant driving experience for you and those around you on the road.

4) Fewer Vibrations

There used to be a lot of vibrations felt in traditional direct fuel diesel engines. Now those vibrations have been reduced with the common rail direct injection system for a much more comfortable driving experience.

5) Better Mileage

bad gas in car symptoms

Since the common rail diesel engine provides more power, that means you will get better mileage on your fuel. As a result, your fuel economy will be better as well. This means less money spent on fuel when you’re on the road.

See Also:  Common Causes of High Fuel Consumption in Diesel Engines

Top 3 Disadvantages of Common Rail Diesel Injection

With all the advantages of the common rail engine, there are some disadvantages as well. Although there are fewer negatives, they may affect your decision of whether to purchase a common rail diesel engine-powered vehicle or not.

1) Higher Vehicle Cost

Ford trucks

Vehicles with a common rail diesel engine are going to be more expensive than those with the traditional direct injection.

If you’re working for a company that supplies you with the vehicle as part of their flee, then it is no sweat. But if it is a personal vehicle, you need to consider whether the extra cost is worth it. For most, it definitely is.

2) Expensive Parts

Since common rail diesels are more expensive, you can expect that replacement parts are going to be expensive as well.

3) More Maintenance

Common rail diesel engines will need more maintenance than a traditional diesel engine. Even if you do the maintenance yourself, it still takes more time, effort, and expense as noted above with the higher cost of parts.


The common rail diesel engine is certainly an advancement in diesel technology that will eventually replace the traditional direct injection system altogether. Perhaps when this new technology becomes more common in every diesel-powered vehicle, then it will become less expensive.

Until then, you will be making an investment into an engine that gives you better performance, better mileage, better driving experience, and promotes an environmentally friendlier agenda.


7 thoughts on “8 Pros and Cons of Common Rail Diesel Engines”

  1. I used to use Euro 4 standard diesel for my Toyota Double cab D-4D engine. Due to economic situation in Sri Lanka, Euro 4 diesel is not freely available. Can I use normal diesel and if I do, what are the precautions I may have to take.

  2. Can Bio-diesel be used in common rail diesels ? If so, at what ratio (diesel to bio-diesel mix) ? I have a Toyota 3 litre D-4D engine Cheers Norm.

  3. Dont forget that with common rail diesels they have a lower compression which in return makes them impacted more when towing (more like a petrol) as there isn’t as much force in the crank. Its noticeable when towing with a D.I. Diesel you dont use as much extra fuel when towing and there isnt a big loss in power compared to a common rail

  4. I love the thick black sooty smoke and knocking of an old in line 6 ALCO- engine. Nothing can come close- MY CARBON FOOTPRINT IS SIZE 13

  5. Having recently bought my first common rail diesel engine after driving with old diesels for over forty years, here are my observations.
    If there is over 100k on the clock then there will probably be problems appearing with the common rail system even if they are not noticeable yet.
    There are so many extra parts that there is a lot more to go wrong.
    It is much more difficult to diagnose problems.
    It is much, much more expensive to repair.
    Conclusion. Common rail diesels are ingenious while they are in perfect condition but not economically viable for the poorer driver who must rely on older second hand vehicles.


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