Question: It seems that fuel has changed recently, not only in price but also in actual value for money; you seem to get less mileage on a litre of petrol and diesel than previously.
A friend and I drive a lot (on average 3 000 km a month) and have started to notice that, since the petrol price increased recently (from about R9,00 to R10,00 a litre), the quality has changed and we are getting fewer kilometres a tank. I drive two petrol cars and a turbodiesel. Have the manufacturers done this to increase spending, or has government given instruction for this hike in fuel consumption?
TRISTAN SPIESS, By e-mail
Answer: An interesting conspiracy theory, but we strongly doubt it. Fuel is strictly regulated and to change the grade of fuel with the intention of making cars use more would be a major technical, logistical and practical challenge (not to mention a huge cost). It is much easier to slap an extra few cents onto the fuel tax and recoup all the money needed without all the aforementioned hassle.
Measuring fuel consumption on the road has some value but it is not really scientific because there are too many variables, including climate, traffic patterns, drive cycles and driving styles. The only scientific way to establish if there are fuel-consumption differences is to run an engine on an engine dynamometer under strictly controlled conditions and compare one fuel with the other.
Our opinion is that the higher ambient temperatures of the summer season lead to hotter air-intake temperatures and result in engines being less efficient. However, the biggest impact on fuel consumption is probably the air-conditioner.