Petrol vs. Diesel: Which is cheaper to run these days?

Jan 20, 2012 by Justin McCall    2 Comments    Posted under: Motoring

I have often been asked, now that I own a diesel vehicle, whether or not it is actually cheaper than owning a petrol vehicle.  With the rising cost of diesel, now a whole R1 more than petrol, people are questioning the savings that were once obtained from purchasing a diesel vehicle.

So, using the vehicle that I own, the Ford Figo 1.4 TDCi (Diesel), I took to Ford’s website and got hold of it’s manufacturer specs and compared the car to the Ford Figo 1.4 Ambiente (the petrol version).  I haven’t included the cost of purchasing the vehicle as there are just too many options in buying the car.  So please be aware that the diesel, in this case costs R14k more than the petrol.

Taking the petrol/diesel price, basic service cost, (which is about the same for the petrol and diesel), doing an average of 20,000km per year, the table below shows that there is a very marginal saving in owning a Diesel over the period of a year. Around R1300.00.

In my mind, it doesn’t really make that much of a difference.  Even on a monthly basis, there is a saving of R111.

On paper, the answer is diesel.  It is without a doubt the cheapest to run of the bunch, but only marginally.  I don’t think this should be a big factor when deciding between petrol & diesel.

However, where diesel wins, is on lower CO2 emissions and the wonderful torque and power you get from such a small engine.  Diesel is a nicer car to drive when you are looking for that extra oomph when overtaking or powering up a hill.

	1.4 Petrol	1.4 TDCi
Tank Size (Litres)	45	45
Fuel Consumption (Litres/100km)	6.6	5.3
CO2 Emissions	156	139
Fuel Cost (Per Litre)	R 10.00	R 11.20
TOAL TANK COST	R 450.00	R 504.00
KM per Litre	15	19
KM’s per tank	682	849
Service Cost	R 1 200.00	R 1 200.00
Cost per KM	0.66	0.59
AVG Mileage	20000	20000
Total Cost Per Year	R 14 400.00	R 13 072.00
Cost Per month	R 1 200.00	R 1 089.33
SAVING PER YEAR on Diesel	n/a	R 1 328.00

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2 Comments + Add Comment

• 
  Paul Cartmel January 24, 2012 at 9:11 am

  1) Diesel isn’t always more expensive. I have had a diesel for the past 6 years and for the most part diesel has been cheaper.
  2) Diesel might need the oil valves and lubrication checked more frequently but the engine is way simpler (no complex ignition timing issues) and generally needs less maintenance.
  3) A simpler engine has a smaller carbon-footprint to produce. Ever seen how large the carbon footprint of the Prius engine is? It simply doesn’t pay itself off over the cars lifespan (and has twice as many parts – most of which (batteries/cables/plastic) can’t be disposed of simply.
  4) The engine revs lower and is thus less prone to the high stress and strain rate failure of high revving engines. Which is why the Diesel cars at Le Mans have always been more reliable and usually win the 24 hour race.
  5) Diesel is more likely to be produced cleanly, extracted from plants or produced from waste oil.
  6) 12% less fuel emissions over the life cycle of the car – that’s huge.
  7) Diesel’s low down torque is a beautiful thing.. especially in the bigger engines (3L+)

  That’s just off the top of my head.

  Ps. As an ex-mech-eng I want to write a post on the thermal efficiency of the diesel cycle http://en.wikipedia.org/wiki/Diesel_cycle vs the petrol cycle http://en.wikipedia.org/wiki/Four-stroke_cycle it’s interesting stuff and illustrates why diesel will always be more efficient.

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  Justin McCall February 16, 2012 at 9:31 am

  Awesome info Paul! Thanks. And I totally look forward to your article.

  Reply