What happens if petrol is used in a diesel engine?

 

  Before going to discuss the answer, we must study these topics first.

1. Flashpoint temperature
2. Auto-ignition temperature
3. Volatility
4. Spark plug
5. Injector 
6. Compression ratio

•       FLASHPOINT TEMPERATURE:

      It is the lowest temperature at which ignition can start if a source is provided.

      So when we see our two liquids,  Petrol has a low flash point temperature, i.e, -43 degrees Celsius, and Diesel has a high flash point temperature of 50 degrees Celsius. That means Petrol can ignite itself at -43 degrees celsius if some source is provided.

•      AUTOIGNITION TEMPERATURE

                 It is the lowest temperature at which ignition can start automatically even if any external source is not provided



Here, Petrol has got the highest autoignition temperature, i.e, around 280 to 310 degrees Celsius, and Diesel has a low autoignition temperature,  around 210 degrees Celsius.

•     VOLATILITY

                It is the tendency of a substance to evaporate at normal temperatures.  Here, Petrol has high volatility and Diesel has less volatility.

•     SPARK PLUG

               It is a device that fits into the cylinder head of an internal combustion engine and carries two electrodes separated by an air gap, across which current from a high-tension ignition system discharges, to form a spark for igniting the air-fuel mixture.


                                

These are used in Petrol engines to ignite the air-fuel mixture but in diesel engines, the presence of spark plugs is not necessary.

• INJECTOR

                An injector is a device for injecting liquid fuel into an internal combustion engine. This is used in Diesel engines as there is no spark plug used.

                                   

• COMPRESSION RATIO

                The compression ratio is defined as the ratio of the volume of the cylinder and its headspace. Petrol engines have a compression ratio  in the range of 10.0:1 to 13.5:1, while diesel engines have a compression ratio  in the range of 15:1 and 23:1


Moving into the main topic:

 What happens if petrol is used in a diesel engine and vise versa?


CASE_1: Diesel used in Petrol engine.

   As diesel is less volatile in nature and requires high compression ratio this fuel will not mix with the air properly and combustion will not be initiated by a spark plug. So it will not cause firing.

                                

CASE_2:  Petrol used in a Diesel engine.

   The temperature after compression in the cylinder of a diesel engine will be very high (as the compression ratio is high in a diesel engine) and when we pour Petrol in it, which is highly volatile in nature this will lead to detonation and your engine components may get damaged.

Source: mikeshawsubaru.com