Additives Keep It Business as Usual with E85

By Keith Corkwell | March 10, 2008
With more than 7 million flexible-fuel vehicles capable of using E85 fuel (85 percent ethanol and 15 percent gasoline) on the road in the United States, industries along the E85 supply chainoil companies, vehicle manufacturers and additive companieshave geared up to address the needs for the new fuel.

Companies entering the E85 arena are finding that it isn't business as usual with this fuel and that all fuel for passenger car vehicles isn't the same. In fact, with E85, challenges abound and production is loaded with complexities.

For years, the fuel industry has blended ethanol into gasoline at low levels (generally 5 percent to 10 percent but up to 25 percent in Brazil) and has blending and operational procedures. Some of this knowledge can be transferred to E85. However, although ethanol offers advantages in the areas of octane, energy independence and as a renewable energy source, there are new technical and operational concerns when higher levels are blended with gasoline. That's where specially formulated multifunctional additive packages can play a role.

Additives Come into Play
From a fuel additive perspective, ethanol-blended gasoline creates some unique challenges. While many traditional gasoline additives have been used for some time in low-level ethanol blends, the industry is just developing a better understanding of the special additive needs of these new higher ethanol blends.

Gasoline typically contains additive packages to improve performance and keep engines clean, and it is tempting to use them in E85. However, the move to higher levels of ethanol in fuel such as E85 has uncovered a host of new engine operation challenges that gasoline additives simply are not formulated to address. The problems that occur when gasoline additives are used in E85 shouldn't be surprising since these additives were never formulated for use in E85.

Intake Valve Deposits
Recent tests have shown that FFVs using E85 can produce engine deposits. In-depth research on the subject is discussed in a Society of Automobile Engineers technical paper published in October 2007 titled "A Comprehensive Examination of the Effect of Ethanol-blended Gasoline on Intake Valve Deposits in Spark-ignited Engines." The good news is that appropriate additives specifically formulated for use in E85 can address deposit problems. However, these additives are different from those used in gasoline.

A series of 5,000-mile tests were run on an FFV using varied mixtures of ethanol and gasoline. The results showed that with no additive present, ethanol impacts the amount of intake valve deposits formed in the engine. At lower levels of ethanol such as E10, intake valve deposits actually increase to higher levels than in gasoline alone. However, in blends with higher levels of ethanol, the level of intake valve deposits actually decreases to the level found in gasoline, or even lower. Gasoline and E10 blends are commonly treated to reduce these deposits for improved emissions, performance and fuel economy. E85, even with its lower deposit impact, should still be treated and does not normally contain sufficient levels of deposit-control additives (Figure 1).





Just as all gasolines vary in their severity and ability to form intake valve deposits, batches of E85 also show various levels of severity. In 5,000-mile tests, three separate batches of gasoline were evaluated for deposit formation. The results were compared to the deposit formation of three separate batches of E85 made from these gasolines. The tests showed that the higher the severity of the gasoline, the higher the severity of the E85 that used that gasoline as its hydrocarbon component. However, E85 produced roughly one-third to one-half fewer intake valve deposits than gasoline alone (Figure 2).



While E85 produced fewer intake valve deposits than gasoline in these tests, gasoline deposits are normally controlled with standard deposit-control additives. Solubility issues preclude using these same gasoline additives in E85. However, specially formulated E85 additives can be used. Figure 3 shows the results of using a properly formulated E85 deposit-control additive in the most severe batch of E85 tested.

Intake Valve Sticking
Intake valve sticking is a possible, unintended consequence of using poorly formulated gasoline additives in gasoline. This occurs when some of the additive builds up in the annular space between the intake valve stem and the valve guide in the cylinder head. At low temperatures, any build-up in this area becomes more viscous and inhibits valve movement. Under extreme conditions, the valve spring cannot close the intake valve, resulting in a loss of compression. Consequently, the engine doesn't start.

Modern gasoline additives are formulated to prevent this problem in normal gasoline. However, recent research has shown that ethanol can make intake valve sticking even more severe and confirms the need to test gasoline additives in the full range of fuels in which they will be used, including the low-level ethanol blends widely available in the U.S. market. More importantly, in the more extreme case of E85, it points out the need for specific additives for E85 that are designed to treat the problems without causing unwanted side effects, such as intake valve sticking.

Combustion Chamber Deposits
Combustion chamber deposits are a secondary concern in gasoline use. Additive packages are formulated to minimize such deposits. Test results shown in Figure 4 indicate that the thickness of these deposits actually decreases as ethanol levels in the blend increase.

Keeping Clean
In most of the world, gasoline contains detergent additives to keep critical engine parts clean. However, most E85 fuel contains very little to no detergent additive. What is worse, many existing gasoline additives are not fully compatible with E85. While they may appear to mix well with high-level alcohol fuels, the additive may not be completely soluble and could fall out of solution or become trapped on fuel filters.

New technology additives specifically formulated for fuels with high alcohol levels are capable of keeping clean the engines running on E85 fuel. They also aid in cleaning those engines. Additionally, the technology works in gasoline or low-level alcohol blends such as E10, so it can remove the deposits in an FFV whether they were created by E85 or gasoline.



Corrosion
Corrosion is a concern with any fuel as it travels through the fuel tankage and distribution system and finally through the vehicle itself. Ethanol can create additional concerns about corrosion. While ethanol is relatively pure, certain contaminants such as acids and sulfates can contribute to corrosion. A properly formulated fuel additive for E85 can address this issue.

It's not business as usual when it comes to E85. E85 is not a traditional fuel, and it requires different additives than those used in traditional gasoline. Multifunctional E85 additive packages need to contain proven components that can keep critical FFV fuel system areas clean and reduce corrosion and deposits that can form on critical engine parts. Luckily, specially formulated E85 additive packages with these capabilities exist.

Keith Corkwell is the regional business manager for gasoline additives for The Lubrizol Corp. Reach him at keith.corkwell@lubrizol.com or (440) 347-5963.