Testing for Ethanol

December 14, 2010

As this topic seems to come up quite regularly and we always have to reference other sites or re-describe how to test for Ethanol in MoGas, I thought I'd put the blog to good use and write up the method with photos, as well as demonstrating actual detection.

All comments and feedback welcome.

How to Test for Ethanol in your Fuel

davidh10

on 14-12-2010 at 02:27

Introduction

Governments are starting to legislate to force Ethanol into ULP (UnLeaded Petrol). In Australia, the New South Wales (NSW) Government has been first off the mark with a mandate to include 10% Ethanol in ULP by December, 2010. The Queensland (Qld.) Government followed suit to implement a 5% mandate.

Both the NSW and Qld. Governments have recently deferred the implementation date (NSW till July, 2012 and Qld. till December, 2011) due to a shortage in the supply of Ethanol. The Brumby Labour Government in Victoria, was proposing to introduce a mandate, however with the change to a Liberal government post the November 2010 election it is uncertain.

Although there are other sources for Ethanol testing information, I thought there should be an article on

Recreational Flying

which can be found easily by members and guests. The topic has already been raised on a number of occasions and as the availability of Ethanol-free ULP diminishes, more people will become interested.

Why should I Test for Ethanol

There's surprisingly many reasons. Here's a list presented in point form:-

Your aircraft may not be certified for fuel containing Ethanol.

If you put Ethanol containing fuel in a certified aircraft, for which the manufacturer has not provided a statement of compatibility, you will be operating outside the law, regardless of whether the Ethanol is harmful to the aircraft.

Your Engine may not be designed for Ethanol.

This may be due to gaskets that swell or decompose in the presence of Ethanol. These days, most modern engines are compatible with some level of Ethanol in the fuel, but without a statement from the manufacturer, you risk malfunction that could range from fuel leaks to engine stoppage.

Your fuel system may not tolerate Ethanol.

Even if your engine is certified for use of Ethanol containing fuel, the engine manufacturer, in all likelihood, does not certify the fuel system including the fuel lines, filters and tanks. Ethanol is known to attack fibreglass tanks and some forms of rubber.

Ethanol is more volatile than petrol.

It is therefore more inclined to evaporate in storage or in the aircraft fuel system. As Ethanol contributes to the octane rating of the fuel, evaporation will reduce the octane rating and may result in lower power output and detonation. Detonation is detrimental to the engine and could result in anything from piston damage to catastrophic failure.

Ethanol is a solvent (cleaning agent).

Ethanol in the fuel will help clean your fuel system. The problem is that the gunk that is dislodged can end up in your fuel filter, possibly causing clogging and engine fuel starvation.

Chemical reaction between Ethanol and chemicals in non-Ethanol containing fuel.

Mixing Ethanol containing fuel with non-Ethanol containing fuel can result in a chemical reaction, resulting in a gel like precipitation.

Ethanol is miscible (soluble) in water.

This can have both a beneficial effect and detrimental effects. Beneficially, it will take up small amounts of water that may be lurking in your fuel tanks or system and pass it harmlessly through the engine.

If however the amount of water is excessive, the alcohol and water may separate out of the petrol into a layer on the bottom of the tank and fuel system components. That layer won't combust, so it has the potential to stop your engine if it gets into the fuel lines. The remaining petrol is now octane depleted and will exhibit the same problems as described above for octane depletion.

The amount of water that can be held in solution in Ethanol decreases as temperature decreases. This could mean that water will come out of solution at altitude when the fuel cools.

Dissolved water in the fuel will support corrosion of susceptible metal parts in the fuel system.

Ethanol in fuel compromises easy water detection.

As described in the point above, Ethanol in the fuel will allow a certain percentage of water to be dissolved in the fuel and thus, by the test methods described here, be undetectable.

Test Method

You will need a graduated container showing volume measurements, and which can have the top sealed. If you are testing just for the presence or absence of Ethanol, rather than to determine the percentage of Ethanol in fuel containing it, then actual measurements are less important than just a volumetric mark. I have chosen in this blog to demonstrate using a laboratory standard, 25 millilitre graduated cylinder. In my aircraft I carry a fuel tester that is calibrated to show Ethanol percentage. I've also seen descriptions of people using just "a jar with a level mark." As you don't want to use a lot of fuel in the test, a tall narrow cylinder is best suited.

If you are using a cylinder that you have sourced and which does not have any volumetric markings, you should prepare it by making a mark about 15% up from the bottom, using a marker that won't dissolve in the fuel.

Fill your cylinder to the mark with clean pure water, viewing the alignment with your eye level with the mark on the container (this prevents parallax error and light refraction introduced when viewing it at an angle).
Now top up the cylinder with at least four times the water quantity of the fuel to be tested. This is important, as you are looking for the possibility of a comparatively small percentage of alcohol in the fuel volume.
You will notice a very distinct colour change at the boundary of the water, at the bottom of the cylinder, and the fuel sitting on top of it.
Seal the top of the cylinder and shake it vigorously for about a minute. The objective is to mix the water thoroughly through the fuel so any Ethanol present will become dissolved in the water.
You will now notice that the fuel / water mixture is quite cloudy. Place the cylinder on a safe solid surface and leave it for a few minutes to separate.
In this picture you can see the indistinct delineation between water and fuel as the components are still separating. The separation occurs much quicker with fuel that contains no Ethanol, however that should not be taken as the indication.
After the fuel / water mixture has separated, you will again see a sharp delineation between the two liquids and the fuel will not be cloudy any more, as the suspended water droplets will have settled back to the bottom.
Observe the water level with respect to the mark that it previously lined up with exactly. If the level has risen, it is because the water volume has increased due to dissolving the Ethanol out of the fuel.
It can be seen that the level of the demarcation is distinct and has not changed, (ie. the same as the water level before addition of fuel) therefore there is no Ethanol in this fuel. :)
The percentage of alcohol present can be calculated as shown below.

Now let's demonstrate Ethanol detection in the fuel.

The first picture is of 5ml of water, before addition of fuel.

Now I have added 19ml of "Plus ULP" from United Petroleum, which is stated to have up to 10% Ethanol and placarded as unsuitable for aircraft. This takes the total level to 24ml.

Shake, as described, to mix the water and fuel well. The result is quite a cloudy mixture as pictured.

After waiting for the mixture to settle and separate, the result can clearly be seen. We started with 5ml of water. The water / Ethanol mixture is now 6.5ml, the total level is unchanged at 24ml and there is now 17.5ml (24 -5 -1.5) of fuel containing no Ethanol. By calculation (1.5 / 17.5 * 100) gives 8.6% Ethanol.

From the above, you can see the sensitivity of the test. Fuel containing 8.6% Ethanol resulted in a change in volume, in this case, of 1.5ml. In this cylinder, you could only be expected to detect a change in volume of about 0.5ml which would correspond to 2.7%. Notice that in the test method section, there were a few drops of water stuck to the cylinder above the fuel. Those will decrease the water volume by a very small amount, and thus produce an experimental error, which effectively reduces the sensitivity of the test. To increase the sensitivity, would require a taller cylinder of the same diameter. Using the same amount of water, double or triple the fuel volume added.

Also refer to the separate blog entry "

[/url]Implications for Water testing of Fuel Containing Ethanol

".

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Caveat:

The author provides this information in good faith and does not warrant this information to be correct. The reader must use their own resources to determine the suitability of this information to their situation and relies entirely on their own judgement in applying this information and in so doing shall hold the author harmless with respect to any and all consequences.

*This Blog and attached Image(s) are Copyright 2010 David Hunt, who grants the "Recreational Flying" Web Site a perpetual, royalty free, non-exclusive and non-transferable license to publish and display on their web site.