The main differences between a petrol and a diesel engine are that the diesel is ‘Compression Ignition’ and the petrol engine is ‘Spark Ignition’. Diesel engines have an ideal air:fuel ratio of 20:1 and Petrol engines have a ratio of 14.7:1. Diesel engines are often cheaper to run than Petrol engines aswell, below are the advantages for both petrol and diesel engines.

Diesel

• No Spark Plugs
• Greater Thermal Efficiency
• Cheaper to run, more economical
• Greater torque output
• Torque output lower down rev range
• More suitable to commercial vehicle
• No ignition system, no high voltage wires avoids the risk of water ingress

Petrol

• Quieter
• Less Vibration
• Lighter than Diesel
• Requires less careful maintenance
• Less Compression Pressure
• Lighter starting system
• Less complex outlay