Internal Combustion Engines
The fuels in order of decreasing knock tendency for spark ignition engines are

Paraffin, napthene, aromatic
Napthene, paraffin, aromatic
Paraffin, aromatic, napthene
Napthene, aromatics, paraffin

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Internal Combustion Engines
Fuel consumption of diesel engines is not guaranteed at one quarter load because at such low loads

The engine is rarely operated
The friction is unpredictable
The small difference in cooling water temperature or in internal friction has a disproportionate effect
The friction is high

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