You wrote: " Also, diesel engines are more complicated than petrol engines and thus require more energy and materials to manufacture." which isn't exactly true. Okay, it's wrong. Diesel engines are essentially a block of iron. Unlike gasoline engines ( and stop calling them petrol. This is an American Bsed website) diesels don't need high tension coils, distributors, spark plug wires or even spark plugs. One of heir charms (and they need them, because they have their downsides) is the comparative simplicity.