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Q.

Why does diesel engine achieve more mileage than petrol?

Tags: science, environment, cars & bikes
Asked by joyesh chakraborty, 12 Oct '09 03:46 pm
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Answers (6)

 
1.

First is that diesel fuel has more carbon in each litre, which is what burns. That means it takes less of it to give the same explosive power in the cylinder, which is what drives the vehicle. Thus you get more work out of the same amount of fuel.

Second, diesels have a much higher compression ratio than an Otto cycle spark-ignition engine. That means there is a greater expansion ratio involved in each explosion, again causing more power.

Thirdly because of fuel injection and CRDI etc..the diesel gets burnt completely before leaving the engine, whereas a portion of petrol leaving with the exhaust is unavoidable in case of a petrol engine..
Answered by MajorVLoganathan, 12 Oct '09 04:04 pm

 
  
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2.

Diesel Engine are more fuel efficient than petrol for just one count. The calorific value of Diesel is more than Petrol and hence the energy output per unit volume of diesel is better than petrol.
Answered by Lucky, 12 Oct '09 04:03 pm

 
  
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3.

A diesel engine runs on a compression ratio which is much higher than a petrol engine. In layman terms it means that more air in the air fuel ratio which goes in the combustion chamber. Since diesel engines work on the compression ignition aspect as opposed to spark ignition gasoline engines, they (diesels) tend to burn the complete fuel in the chamber. Hence diesel engines are more fuel efficient than petrol (gasoline) ones.
Source: http://www.automotix.net/autorepair/engine_repair_guide.html
Answered by Arnold Connery, 08 May '13 06:44 pm

 
  
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4.

I think petrol engine gives better mileage.
Answered by Damodar Biswal, 12 Oct '09 04:00 pm

 
  
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5.

Diesels can reach more mileage than their petrol counterparts as it light
Answered by saranathan Narasimhan, 12 Oct '09 03:49 pm

 
  
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6.

A diesel engine has more torque, requires less rpm's, and can be built smaller with reduced weight than a petrol one with spark plugs. Diesel fuel has more energy (BTU) per litre than petrol.
Therefore, all other things being equal, the diesel engine will get better fuel mileage.
However it may be noted that a petrol engine is always more powerful than a diesel engine !
Answered by prasoon, 13 Oct '09 12:17 pm

 
  
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