1. In diesel engine, fuel used is diesel oil.
2. In this engine, fuel is burnt inside the cylinder.
3. The power in diesel engine is derived from hot gaseous products obtained by combustion of diesel.
4. It is relatively safe.
5. Its efficiency is higher (about 40%).
6. It can be started almost immediately.
7. It is relatively compact and can be used in lighter vehicles such as cars, buses, etc.
External Combustion Engine
1. In this engine, fuel used is coal.
2. In this engine, fuel is burnt outside the cylinder and is used to produce steam. Steam is then introduced in the cylinder.
3. The power in the steam engine is derived from steam under pressure.
4. It is relatively unsafe due to the high pressure of steam.
5. Its efficiency is low (about 20%).
6. It cannot be started immediately; therefore, it has to be kept running.
7. It is very and cannot be used in cars, buses, etc.