One of the biggest myths about biofuels is that they can increase a vehicle’s fuel consumption dramatically.

In fact, ethanol only reduces your fuel consumption by around 1-3%, which is very low compared to many other factors that impact on how efficiently your vehicle runs. Plus, the higher octane rating of ethanol compared to standard unleaded can help vehicles to run more efficiently – which can negate the potential increase in fuel consumption in some vehicles.

If you do notice that your fuel consumption is unusually high when running on ethanol, there could be a simple explanation. There are also simple and relatively inexpensive ways to address any issues.

Try changing your fuel filter after using E10 the first few times – ethanol is a powerful solvent that can loosen old fuel deposits in the fuel system

  • Remember that ethanol is hygroscopic; if there was water in your fuel system, the ethanol in your fuel may have taken it into the blend. Once this tank of ethanol is finished however, any rough running should cease
  • Get your vehicle serviced if this hasn’t been done recently, to ensure all the components of your fuel, ignition and engine management systems are running correctly.

A number of other factors can affect how much fuel your car uses. We’ve summarised some of these below – and you might be amazed at just how big an effect they have.

  •  All types of fuel can affect your fuel consumption. In fact, the variation between different brands, batches and even seasonal supplies can increase fuel consumption by around 5%.
  • Checked your tires lately? Under-inflated tyres can increase your fuel consumption by 5%. If your wheels are out of alignment, add another 10%.
  • Has your vehicle been serviced recently? A clogged air filter can increase your fuel consumption by 10%, and a faulty oxygen sensor by 40%.
  • How are you driving? Heavy acceleration and braking can increase fuel consumption by around 30%. Just by increasing your speed from 100km/h to 110km/h, for example, you can increase fuel consumption by 10%.
  • Is it hot outside? Using the air conditioner can increase fuel consumption by between 10 and 20% – but driving with the windows down has a similar, albeit less drastic, effect on fuel economy.
  • Speaking of temperature… Driving into a 30km/h headwind can affect your fuel economy by 5%. Add cold weather into the mix and there can be an increase of up to 10%.
  • Heavy traffic, rough surfaces and wet roads also impact fuel economy, while fully-loaded roof racks add around 30%.

Compared to these examples, and after taking into account lower prices per litre and ethanol’s higher octane rating, ethanol’s impact on fuel consumption is negligible.