With fuel prices rising to all time highs, one issue that has come to a head, especially here in Australia is the contraversial topic of pump fuel blended with Ethanol.
From an economic point of view it makes sense, as mixing in locally produced Ethanol reduces the amount of expensive foreign crude oil required. Blended fuels are not a new development, as Sweden and the US have been using 10% mixes for many years successfully. In Brazil, it is illegal to sell pump fuel that has less than 20% ethanol content. Granted, Brazil was the last country in the world to finish producing the original Volkswagen Beetle, in itself not exactly a paradigm of high performance or modern tehnology, it is plainly evident high levels of Ethanol doesn't seem to create too many issues. And certainly not the sorts of wild predications of doom and gloom for your motorcar as portrayed by some of the Australian media.
In actual fact, ignoring the hype, there are four main areas of concern with 10% Ethanol blends:
- Water - Ethanol has a great affinity with water. Most metal components in fuel systems will corrode or rust in the presence of water. Fuel blended with 10% Ethanol will increase the quantity of water it can absorb without separating out. It is important to note that the addition of Ethanol doesn't suddenly create water out of nowhere, but tends to "pickup" water more easily throughout the transportation and storage phase of its distribution to end users. It is generally accepted that 10% blends do not pose a significant risk of fuel system corrosion in everyday use, as Ethanol blends have increased quantities of anti-corrosion additives found in normal un-blended fuels.
- Fuel System Contaminants - 10% Ethanol blends can cause problems with cars that already have a heavily contaminated fuel system to begin with. Ethanol can act like a solvent, scouring gum, varnish, dirt and water from the insides of fuel tanks and fuel lines, leading to clogging fuel filters more regularly until contaminants are cleaned from the system.
- Material Incompatibility - Older cars can be at risk of accelerated wear of rubber, cork and certain plastic fuel system components, but these very same components are equally at risk when used with fuels containing high levels of toluene, the additive primarily responsible for improving the octane rating of unleaded fuel.
- Fuel consumption - Ethanol has a lower energy content when compared to petrol, requiring a slightly higher volume of fuel to be burned in order to provide the same amount of power. In theory, an engine using a 10% blend should consume 3.8% more fuel. This is somewhat offset by a sligh improvement in efficiency, but is very much dependant on the type of engine.
Now for the good news. As demonstrated by the fuel tests, significant performance gains can be made by using a 10% Ethanol blend. This is becuase Ethanol is an oxygen rich fuel, and this assists with improving the combustion process. Most importantly the addition of Ethanol improves resistance to detonation, which is good news in a turbocharged car such as the WRX and Evo. The ECU in the WRX will respond to improved fuel quality and will increase the maximum amount of ignition advance generating more power. As a general rule of thumb, 95 RON unleaded fuel blended with 10% Ethanol will achieve an octane rating of between 97.5 and 98.5 RON.
Performance Tuning for Ethanol blends
Highly stressed engines would benefit from a dyno tune and check if switching to an Ethanol blend. Typically airfuel ratios will go slightly leaner,s omewhere in the vicinity of 3-4%, requiring slightly more fuel so as not to compromise engine safety.
Subaru and the Ethanol debate
Going by a press release listed on Subaru Australia's website, all Australian delivered Subarus built after the 1990 model year are compatible with Ethanol blended fuels up to a maximum 10% blend. This compatibility extends to a maximum of 10% only, and comes with an important caveat, warning that damage could result from the use of fuels containg more than 10% will not be covered by new car warranty. Pre 1990 delivered Subarus have not been tested with Ethanol blended fuels and as such are not recommended for use with these early cars.
There are some important exceptions: Liberty B4s, Liberty GT 2.0L and Impreza WRX STis MY99 to MY05 may experience starting and / or driveability concerns if Ethanol Blended fuel of any level is used and therefore is not recommended by Subaru for these cars.
Mitsubishi and the Ethanol debate
According to the FAQ on the Mitsubishi Australia website, all Mitsubishi vehicles built since 1986 are fully compatible with up to 10% ethanol fuel in the mixture, provided the octane rating is at least as high as that recommended for unleaded petrol. If your car was built prior to 1986 or you are unsure of its age, please contact Mitsubishi Australia.