Diesels have disadvantages. They are hard to start in cold weather. Their acceleration is sluggish. They are noisier and smellier than gasoline engines. This is the diesel engine process:

1. Air is drawn into the cylinders. The piston squeezes, or compresses, the air up to the top. Compressing the air makes it very hot.

2. At the same instant, a valve sprays diesel fuel into the top of the cylinder. Heat from the compressed air sets fire to the fuel.

3. The exploding fuel makes a lot of pressure, which pushes the piston down.

4. The up and down movement of the pistons turns the crankshaft, just as it does in a gasoline engine.

5. A valve at the top lets out the waste gas, and the cylinder takes in more air for the next stroke.

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