One of the main problems with a diesel engine is the loud sound that the engine produces. This sound is produced by the fuel igniting inside the engine. The engine makes more sound than a traditional fuel engine because the fuel is filtered less and has more particles inside the fuel. Older diesel engines are usually much louder than new engines, because newer technology has enabled the engines to run much softer. You can help reduce the amount of noise the engine makes by making a few modifications to oil, fuel and insulation.
Switch out your regular diesel oil for noise-reducing oil. Choose oils designed to reduce diesel engine noise with the addition of agents inside the oil designed to eliminate some of the noises produced by loud diesel engines. You can find noise-reducing oils at most auto supply stores.
Choose fuel that has the cetane number recommended for your diesel engine. Your car or truck's operating manual will specify what cetane number or rating is recommended for your engine. Choosing fuel with that cetane number will help eliminate much of the loud diesel engine noise by changing the ignition delay and reducing the noise produced by the engine.
Install a sound-dampening hood mat under the vehicle's hood to absorb the noise produced by the engine. These insulating mats are inexpensive, and most clip to the edges of the hood or are installed with automotive adhesive. This will muffle much of the sound produced by a loud diesel engine.
Replace the rubber seals around all of the doors and windows inside the vehicle. This will help reduce the amount of engine noise that you can hear inside the vehicle. For most cars and trucks, the rubber seals will simply slip off with the use of a flathead screwdriver. You can then slide the new seal back over the doors and windows to reduce the amount of sound heard inside the car.