Difference between Diesel and Petrol Engine

Petrol and diesel engines are two common things used internal engines. Petrol and diesel engine is done on basis of fuel used by these engines. Engine which uses petrol is called petrol engine but engine that uses diesel is called diesel engine. In this article, we will discuss about differences between petrol and diesel engine.

There is lot of variation between diesel and petrol engine are as follows. Here will discuss all the main differences among these engines. Check What is a Dynamometer?

  • Diesel engine is compression Ignition (CI) and petrol is Spark Ignition (SI)
  • Petrol engine works on Otto cycle where as diesel engine works on diesel cycle.
  • In petrol engines air and petrol are mixed in carburetor and it enters into cylinder.
  • But in diesel engines, first fuel goes into cylinder by fuel injector and then gets mixed with air inside the cylinder.
  • In petrol engine first compression of petrol and air is done and then it is charge by an electric spark. In diesel engine only air is compressed and charge by heat of compressed air.
  • However, compression ratio in petrol engine is low as compared with diesel engine.
  • In petrol engine power developed is low due to lower compression ratio while in diesel engine power developed is more due to higher compression ratio.
  • Diesel engine is fixed with fuel injector where as petrol engine is fixed with spark plug
  • Diesel engine has less volatility of fuel is burnt but in petrol engine fuel that burns has high volatility
  • Petrol engines are used in light weight vehicles like car, motorcycles, scooters etc. In diesel engines are used in heavy vehicles like buses, trucks etc.
  • In petrol engine thermal efficiency is up to 26% and diesel engines has thermal efficiency is about 40%.
  • Due to low thermal efficiency, overheating problem is more in petrol engine. However, in diesel engine overheating problem is less due to high thermal efficiency.
  • As compression ratio is low, petrol engines are cheaper and lighter in weight. But in diesel engines compression ratio is high, so these engines are costlier and heavy in weight.
  • Therefore, cost of petrol engine is high because of higher cost of petrol fuel. And diesel engine is low cost because of diesel fuel is lower cost.
  • In petrol engine maintenance cost is less while in diesel engine maintenance cost is more. Also Read How Anti-lock Braking System (ABS) Works.
  • Petrol engines are high-speed engines whereas diesel engines are low-speed engines.
  • There is less starting problem in petrol engine as compared with diesel engine. Also Read Torque Converter Working, Principle, Main Parts and Application.
  • Diesel engine pulls heavy loads easily than petrol engine. Also, diesel engine carry heavy loads to longer distances. Check Brake System Types, Functions, and Types of Brakes in automobile
  • Diesel engines may also need glow pugs in cold conditions which heat up cylinder so that cold engine can start easily.
  • Diesel engines give better mileage than petrol engines. So diesel is much cheaper than petrol.