​Ethanol (E85): Should You Use Ethanol Blends in Your BMW?

Using E85 Ethanol Blends in BMW’s: Should You Do It?

A quick Google search will reveal that there is no shortage of debates regarding the use of ethanol fuel. However, most articles focus on the sustainability and feasibility of ethanol fuels. Although sustainability is important to consider, the real question is whether or not higher ethanol mixtures increase engine longevity and performance in the long-term.

What is E85 Ethanol Fuel?

Before diving into the real question, I will start by giving some background on ethanol (e85) fuel. E85 refers to an 85% ethanol to 15% gasoline mix; most ethanol fuels are corn-based, and as such, E85 is considered to be a renewable fuel. As the impending consequences of global-warming loom around the corner, the United States government passed a mandate to require increasing amounts of ethanol in gasoline. Gas in the U.S. contains roughly 10% ethanol, and 90% gasoline; in other words, the gas that you fill up with at the pump is E10. Although ethanol is considered a renewable fuel the argument against e85 is the heavy demand it puts on water, soil, and food-supply.

E85 Ethanol Effects on Fuel Economy

BMW is one of the most sustainable and environmentally friendly automotive manufacturers in the world. However, for the true car enthusiast, this is only an additional benefit as most enthusiasts buy a BMW for one reason, to own the “Ultimate Driving Machine”. At first glance, it would appear as if ethanol would decrease power output because the British Thermal Units (BTU) rating is less than that of gasoline. A higher BTU rating indicates that gasoline creates more energy per molecule as compared to ethanol. However, e85 requires a higher amount of fuel (more molecules) to reach stoichiometric combustion, which means the overall BTU rating for each burn cycle is higher than that of gasoline. To put this simply, e85 has a higher octane rating than gasoline. On the downside, more fuel is required for each burn cycle, so e85 will actually lower your fuel economy.

E85 Ethanol Effects on Horsepower and Engine Longevity

Enough with the technical gibberish; what does this mean in terms of engine performance and longevity? E85 requires about 30% more fuel for combustion, which means internal cylinder temperatures will be reduced. Because air is denser at cooler temperatures e85 will allow for more air molecules in each cylinder, leading to an increase in horsepower. However, this is only one benefit of cooler cylinder burning temperatures. Heat is what puts stress on engine internals, so less heat will reduce the stress inside the cylinder. In addition, since e85 is harder to burn it will actually reduce the likelihood of engine knocks, pings, and misfires. This allows you to target more aggressive cylinder timing, which will also increase engine performance.

What You Need to Know Before Running E85 on Your BMW

Before running e85 mixtures here are a few things to consider:

-Does your BMW have direct injection? Since e85 requires 30% more fuel for each burn cycle, your fueling system must be capable of delivering enough fuel. Direct Injection is capable of supplying more fuel

-Does your BMW have stainless steel fuel lines? There are also debates on whether or not e85 will degrade fuel lines, seals, etc. To be on the safe side, I would recommend having stainless steel lines and injectors. Most newer, turbocharged, direct-injected BMW engines feature stainless steel lines and injectors that will not be affected by ethanol.

-Do you have aftermarket software? Your ECU/DME will also need to be able to flow more fuel. A stock BMW DME will be able to run mixtures around E20 without any issues. Aftermarket software and tuning will allow most direct injected BMW’s to run around E40 fuel before the low-pressure fuel pump cannot flow any more fuel.

As a fair warning, once you start running e85 there is almost no going back! Within months of using E85 I could tell my engine was running stronger, healthier, and cooler. Although E85 has great performance benefits, there is much more to it than simply putting E85 in the tank and expecting your car to perform better. To anyone interested in running E85 I would suggest doing a lot more research and ensuring you have the proper fueling system, modifications, etc. before fueling up with e85.

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By | 2017-06-11T22:57:18+00:00 June 2nd, 2017|N54 Maintenance, N54 Tuning Guides|0 Comments

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