ALT-4 What are the Differences between Diesel and Gasoline Engines
The most obvious difference between diesel and gasoline or petrol engines is the way they ignite the fuel. In a gasoline engine fuel vapor is ignited at the precise moment by a spark. In a diesel engine the diesel fuel is ignited by a combination of pressure and temperature, no spark is needed. In theory the diesel engine is simpler as there is no need for the complex electronics that gasoline engines need for the ignition system. Diesel engines do however have a much more complex fuel system, running at higher pressure, and have to withstand greater forces so tend to be heavier engines. They also need to have a larger cylinder capacity to create the same power as a gasoline engine so tend to cost more to purchase. Traditionally diesel was a fuel for large car engines and commercials although normal size cars are now being offered as diesel.
Diesel and gasoline are both products from oil, however diesel is the heavier fraction, which means it is a denser liquid. Where as gasoline is extremely flammable and can be lit by a spark, diesel is much harder to ignite, hence the need for a pressure based ignition system. Gasoline engines, because of the volatility of the fuel are by nature more responsive and give better acceleration, although diesel engines can be improved by the use of turbochargers, virtually all modern diesels are turbocharged these days.
Diesel fuel has a higher calorific value, that is to say that you get more heat energy from 1 litre of diesel than from 1 litre of gasoline. This does mean that the fuel economy of diesel is greater. Gasoline is a cleaner burning fuel, and leaves less residue than diesel.
In summary a Diesel engine will be more expensive to purchase but cheaper to run. Gasoline engines are more responsive, but less reliable and have more parts to go wrong. Ultimately neither is superior, it all comes down to personal choice as to which you prefer and if the vehicle you want is available in both engine types.
