E10 Fuel Economy

Ethanol contains less heat energy per litre than petrol, therefore E10 will theoretically increase fuel consumption by just over 3%. However, ethanol has a higher octane rating (129RON) than petrol so the addition of 10% ethanol to regular unleaded petrol (ULP) raises the Research Octane Number (RON) from 91 to 94-95. This improved anti-knock characteristic can allow an engine to operate with greater efficiency. The ability of an engine to use the extra octane efficiently depends on the design and calibration of its engine management system.  Ethanol also cleans fuel systems and burns more completely, reducing the build-up of carbon deposits and providing long-term benefits.

A trial undertaken in 1998 for the Federal Government in a range of Australian vehicles showed that the use of E10 in vehicles designed for ULP increases fuel consumption by an average of 2.8%, however there was considerable variation between individual vehicle models.

There are many other factors that influence fuel consumption:

Petrol

• Variations between petrol brands/batches – up to 5% difference
• Lower energy content of winter fuel – 5%

Driving Conditions

• Traffic density – add 15% in heavy traffic
• Road conditions – hills, corners, loose surfaces, and wet roads all increase fuel consumption significantly
• Ambient temperature – up to 10% increase in cold weather
• Head winds – 5% increase into a 30 kph headwind

Driving Habits

• Speed – add 10% or more if you speed up from 100 kph to 110 kph
• Aggressive acceleration – up to 20% increase
• Air conditioner use at low speed – add 10-20%
• Windows open at high speed

Vehicle Maintenance

• Tuning and engine maintenance. Clogged air filter 10%. Faulty oxygen sensor 40%.
• Tire pressure – 5% increase if your tires are under-inflated
• Wheel alignment – up to 10%

Vehicle Load

• Unnecessary weight in the vehicle – 45kg can mean a 2% increase
• Roof racks – add 5-10% empty, up to 30% loaded up
• Towing

These factors affect fuel consumption much more significantly than the slightly lower energy content of E10.

The final cost outcome depends on the relative prices of the two fuels. Say you drive an average car and experience a 2.8% increase in fuel consumption on E10.  With current petrol prices (22 Jul 09) at approximately $1.10 per litre for ULP and $1.07 per litre for E10, ULP is 2.8% more expensive than E10.  Actual fuel costs for ULP and E10 are therefore about equal for the average car.

E10 has the additional benefits of:

• reducing greenhouse emissions by 3%,
• reducing cancer-causing particulate emissions by 33%,
• reducing petrol imports by 7%,
• creating regional development and jobs in regional communities, and
• creating new opportunities for farmers and foresters .

As Australia’s oil stocks continue to decline and oil prices inevitably increase in the future, biofuels will provide a cheaper local alternative to imported petroleum.