Diesel vs Petrol

Reading Jake Venter’s article on diesel engines in the August 2010 issue of FOCUS got FRANK BEETON thinking about the relatively short period that this form of propulsion has dominated the road transportation scene.

Although Rudolph Diesel’s first engine ran as far back as 1894, it was only during the First and Second World Wars that diesels started to gain popularity in Europe for the heavier automotive applications, and they did not completely displace petrol-fuelled engines from most commercial vehicles until well into the last quarter of the 20th Century.

In South Africa, most of the automotive diesels that entered operation before 1939 were found in city buses. City Tramways in Cape Town and the Durban Corporation bought fleets of British Daimler double-deckers fitted with Gardner diesels – more commonly known back then as “oil engines”. The Gardner, had a legendary reputation for reliability and fuel economy, and was developed from a marine engine design, and it was as a marine engine that diesel technology found wider acceptance. The arrival of World War II halted progress towards broader diesel market approval, when the British Government diverted several Daimler buses ordered by the Johannesburg Municipality to bomb-ravaged UK cities. Other local operators encountered difficulties in obtaining supplies of new vehicles and parts from overseas, and were obliged to buy petrol-engined American-sourced “stop gap” vehicles during the hostilities to maintain their operations. Pretoria’s municipal bus fleet, for example, commissioned a number of buses built on Federal truck chassis during 1939-45.

After the war, the use of diesel became more widespread, but petrol-engined heavy vehicles retained their popularity in the local market. The oil companies bought numbers of International L- and R-Series haulers to draw their fuel delivery tanker semi-trailers, and did so throughout the 1950s. The central South African government and downstream public sector entities persisted with their preference for petrol-engined trucks of up to seven tons payload capacity. This lasted until the early 1980s when General Motors was still importing substantial numbers of petrol Bedfords to satisfy state tender requirements. Private operators also continued to buy petrol-engined commercials for lighter applications well into the 1970s when Chrysler’s Dodge D500 5-tonner was particularly favoured for medium-distance high speed duties such as newspaper delivery.

The final death knell for heavier petrol-engined trucks was sounded by the dual fuel crises that came during the 1970s. These unexpected events caused the price of fuel to soar and focused attention on the greatly superior fuel consumption characteristics of diesel engines, despite generally higher technical complications and the requirement for specialist maintenance of their fuel injection systems. Small displacement diesels were also starting to shake off their earlier reputation for unreliability under heavy traffic and stop-start conditions, and an increasing number of operators were being attracted to the value-for-money products being offered by the importers of Japanese brands.

Towards the end of the 1980s, petrol engines had all but disappeared from commercial vehicles of over 3 500 kg Gross Vehicle Mass, and diesel power was becoming more commonplace lower down the payload spectrum. The emergence of democratic rule in South Africa cancelled out earlier government efforts to discourage the purchase of diesel-powered cars and light commercials, thus allowing the local market to exercise its natural preferences.

Ironically, the world’s preoccupation with air pollution and reduced dependence on fossil fuels early in the 21st Century has tended to refocus attention on spark-ignition engines for trucks and buses – although the latest trend is towards the use of natural gas and biomass-derived fuels, and not gasoline, in these power units.

Europe continues to champion the diesel as the logical solution to these challenges, whereas America has been increasingly drawn to exploring hybrid petrol/electric and pure electric power solutions. Experts agree that the ultimate direction will lead the world to clean hydrogen-powered technology, just as soon as problems with generation, storage and distribution of liquid hydrogen have been solved in a cost-effective manner.

Rear-view Focus is a column by FRANK BEETON that takes a nostalgic look at the truck and bus world of yesteryear. Visit www.focusontransport.co.za to comment on the column and share your memories with us.