E85 – Why is it so popular

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E85 is probably the most popular fuel for high performance engines on the market today. If you go to a race track anywhere around the country you are almost certainly going to smell the sweet smell of the E85 burning, but what is E85 and why is it so popular?


E85, like E10, is a blend of ethyl alcohol (ethanol) and unleaded petrol. The ethanol itself is an oxygenated alternative fuel that is derived from renewable resources such as sugarcane, sorghum and grain crops. It is then processed, distilled and blended with unleaded petrol in different ratios depending on the end product required, ie: E10 (10% ethanol & 90% unleaded petrol) and E85 (85% ethanol & 15% unleaded petrol). Ethanol fuels have been somewhat utilised in the automotive industry since the 1800’s, including Henry Ford’s first vehicle the “quadricycle” in 1896, but they have only become mainstream in Australia during the past 2 decades.


E85 provides a number of benefits over unleaded petrol and some purpose built race fuels for that matter. It is also readily available at selected petrol stations around the country.


Due to its high RON rating E85 reduces the potential for detonation (pinging) making it ideal for use in high compression and forced induction engines. The typical RON rating of E85 that is available at the pump is approximately 105 RON and it is comparable in price to premium unleaded petrol. There are some race fuel manufacturers that produce E85 with higher RON ratings up to about 115-120 RON, which are far more expensive.


The ethanol in E85 is oxygenated and because of this E85 has the ability to be successfully run at far richer air/fuel ratios (as per all alcohol fuels) which produces more power when combusted. Alcohol based fuels such as E85 also have a cooling effect and due to this the intake charge is more dense with fuel and oxygen which again produces more power per combustion cycle.


V8 Supercars now run E85 as a control fuel.


While this all sounds great, ethanol blends such as E85 definitely have their disadvantages too. One of the main disadvantages is that ethanol blends all contain less energy by volume when compared to straight unleaded petrol. E85 typically has 25.2MJ/L whereas unleaded petrol has about 34.8MJ/L which means that to achieve the same power output an engine will need about 40% more E85 by volume. This normally means a larger capacity fuel delivery system needs to be installed into the vehicle and the engine will definitely need to be tuned specifically for E85 unless it has a ‘flex fuel’ system fitted to it such as some of the current Holden Commodore  & Holden Captiva range.


Another drawback is the potential for fuel system corrosion, but not from the ethanol itself, from water! Ethanol is hygroscopic which mean that it pulls in and holds water molecules. The big problem here is vehicles that have steel fuel tanks and fuel lines. The water in the ethanol will cause rust to occur if left in contact with these steel fuel system components over time.


Seal and hose compatibility can also be an issue in some vehicles. This problem is usually restricted to older vehicles that were designed before ethanol fuels became main stream, the same could be said for the steel fuel tank and fuel lines.


Some elastomer materials (rubber) used for fuel hoses, o-rings and gaskets can be affected by alcohol based fuels such as E85 and the result can be in the form of swelling or degradation of the rubber material, so just be sure to check with the manufacturer of the vehicle or fuel system components before using E85.



Some big power gains have been seen in the forced induction world, including up to 50% increase in an XR6 turbo by upgrading the fuel system and tuning for E85 alone. While in other cases when you are talking N/A v8 motors the gains are much less. E85 defiantly has its place in the automotive world, the more common it becomes on Australian roads depends on the education process with owners and tuners alike.


If you do decide to make the switch to E85 and your vehicle is capable of running on it there are extra measures you can take to ensure that the transition is a smooth one, the first is using the correct engine oil. Make sure you choose an engine oil that meets API SN performance specifications as there are additives specifically designed for ethanol compatibility that have been blended into these engine oils. There is also an emulsion retention test that API SN engine oils have to pass in order to verify their ability to manage the water that is brought in from the ethanol fuel and avoid separation in the sump or reservoir.


Another good idea is to use a fuel system cleaner additive on a regular basis when using E85 to ensure that any deposits in the fuel system such as gums and varnishes are kept at bay. Fuel system cleaners also help in dispersing the water from the ethanol fuel which will assist in reducing corrosion in the fuel system.

Stay tuned for the next article on Ethanol fuels coming soon




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