Re: Itain't necessarily so!
The thing to remember with both petrol and diesel engines is that the technology has changed a very great deal in the last couple of decades in both cases.
Diesels have changed from indirect injection using mechanical injectors to direct injection using piezoelectric transducers to modulate how much and when the fuel is injected; modern diesels also use variable vane turbochargers. The net effect is to spread out the torque and power curves, so that diesels are efficient and powerful at a wider range of speeds.
Petrol has if anything undergone an even greater series of changes. Old-style petrol engines used carburettors to produce a petrol-air vapour which was then sucked into the engine. This vapour had to be sufficiently concentrated to ignite from a spark (hence the choke on earlier designs, to enrich the mixture when the engine was cold). This changed to injection into the intake system, and then to the modern, direct injection systems.
These inject petrol directly into the cylinder, but vary the mix so that there is a blob of richer mixture next to the spark plug, and leaner, less rich mixture elsewhere. Combined with a turbo this makes these direct injection engines very, very fuel-efficient indeed.
Toyota hybrid engines have another trick: they are not Otto-cycle engines but are Atkinson cycle engines, which means that more power is gotten out of the petrol combustion cycle, at the expense of somewhat reduced power and torque.
Jaguar recently went one better with a prototype gas turbine engine, which used gas turbines to generate power very efficiently to drive electric wheel motors, with a battery pack in between to smooth the power flow. This works and indeed a US truck company is selling LPG-fuelled gas turbine electric transmission replacement systems, but the problem here is the high cost of the gas turbine engines, which are uneconomic for passenger cars.