Statement (I): A good CI engine fuel, like diesel oil, is a bad SI engine fuel and a good SI engine fuel, like petrol. is a bad Cl engine fuel.

Statement (II): A good CI engine fuel requires high self-ignition temperature and a good SI engine fuel requires low self-ignition temperature.

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ESE Mechanical 2015 Paper 1: Official Paper
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  1. Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
  2. Both Statement (I) and Statement (II) are individually true and Statement (II) is NOT the correct explanation of Statement (I)
  3. Statement (I) is true but Statement (II) false 
  4. Statement (I) is false but Statement (II) is true 

Answer (Detailed Solution Below)

Option 3 : Statement (I) is true but Statement (II) false 
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Detailed Solution

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Explanation:

A good CI fuel like diesel oil requires high self-ignition temperature when it is used in SI engines which are not achieved in SI engine due to this unburnt fuel particles are left inside the engine block so it is not a good fuel for SI engines.

Similarly, a good SI fuel like petrol requires a high self-ignition temperature to avoid knocking before normal combustion occurs.

And for CI engine, a low self-ignition temperature is required as it starts combustion by the only compression.

So, statement 1 is true and statement 2 is false.
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