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Author Topic:   Testing Blended Gasoline for Ethanol Content
jimh posted 11-18-2007 03:55 PM ET (US)   Profile for jimh   Send Email to jimh  
Please use this thread for any follow-up questions or comments on my recent article in the REFERENCE section

Ethanol Fuel Testing
Determining ethanol content in blended gasoline fuels

The article describes a simple test procedure for determining the ethanol content of blended gasoline fuels.

glen e posted 11-18-2007 05:10 PM ET (US)     Profile for glen e  Send Email to glen e     
Thanks Jim - just posted the link on my site, naturally giving you credit...nice work....
highanddry posted 11-19-2007 12:38 AM ET (US)     Profile for highanddry  Send Email to highanddry     
I have been using the EAA method (as I am an EAA Tech Counselor) for many years and it is quite effective.
kgregg posted 11-19-2007 09:21 AM ET (US)     Profile for kgregg  Send Email to kgregg     
Great info Jim! I need to perform this test on 15 gals of suspect fuel in my boat.


TRAFFICLAWYER posted 11-19-2007 12:58 PM ET (US)     Profile for TRAFFICLAWYER    
I wonder if an additive was added to the mix ie, Startron,Stabil,etc., how the outcome of water aborbtion percentage would be affected?
poker13 posted 11-19-2007 07:21 PM ET (US)     Profile for poker13    
Thanks for that very useful article. I'll start testing the gas sold around here soon.
JMARTIN posted 11-19-2007 07:45 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
Pretty cool test, simple and cheap. I must play devils advocate since I am in the fuel business. Fortunately, I am in an area where I do not have to sell or buy gasoline with ethanol in it.

Let us say you want to know if the neighborhood station has ethanol and what percent it is. There are no labels and they will not tell you. Soooo, you pull out your little test kit. Oh, Oh, against the law to put gasoline in a glass container. Even if you can sneak a little for the test, better be carefull with your discarding of the sample because some one will have a conniption fit if they see you dumping it out. So break ou the UL certified gas can, get a sample and go home to do the test. Hooray, it's a good test. Dump your sample on some weeds and scurry back to the gas station to fill up because the next load of fuel they get might be different. John

jimh posted 11-19-2007 08:23 PM ET (US)     Profile for jimh  Send Email to jimh     
You can also get a ethanol fuel test kit from Briggs and Stratton. The part number is


You can purchase the Briggs and Stratton product at a local dealer or at on-line sellers like

The MSRP is a modest $5.65, although shipping and handling charges may increase the cost somewhat.

If you want to use a graduated cylinder, you can often find them for sale at photography supply stores, or at many on-line sellers like these: cylinder&ie=UTF-8&oe=UTF-8&um=1&sa=N&tab=wf

jimh posted 12-01-2007 02:09 PM ET (US)     Profile for jimh  Send Email to jimh     
I have received one email comment that the Briggs & Strattton tester was purchased and found suitable for the purpose. It looks like the lowest-cost solution, other than a generic graduated cylinder.
E4ODnut posted 06-02-2011 10:11 PM ET (US)     Profile for E4ODnut  Send Email to E4ODnut     
This is another fascinating thread I dredged up on a search, but I have some questions.

In theory, at least the way I understand things, the formula %=D/Fx100 should yield the same results regardless of the proportions of fuel to water in the test cylinder.

I did some research on similar test procedures and found proportions recommended for F/W are from 90/10 all the way to 50/50.

In my tests, with identical cylinders, the test results vary quite a bit depending on proportions, which brings in to question, which is the more accurate?

Before I get into specifics, is there any one out there who would like to enter into a discussion and compare test results?


jimh posted 06-03-2011 09:27 AM ET (US)     Profile for jimh  Send Email to jimh     
Thanks for the interesting follow-up on the test procedures. As I said, I am not a chemist, but I will offer the following observations.

When you intentionally add water to the blended fuel, you must add enough water to be certain that the resulting solution of fuel and water will have so much water that there is no possibility of the water remaining in solution with the gasoline. As I understand it, the solubility of water in gasoline is limited to about 0.5-percent by volume. If you increase the water so that it is 10-percent by volume compared to the gasoline, you have a situation where the concentration of water is now 20-times greater than its solubility in gasoline. This should be enough to drive out any of the alcohol in the gasoline.

If you increase the concentration of water to 50-percent, you have exceed the solubility by a factor of 100-times. I don't know if a difference between super-saturating the gasoline with water at 20-times solubility compared to 100-times solubility will have an influence on the outcome. In either case, it seems like the most water that could remain in solution with the gasoline would be 0.5-percent. It is hard to read the graduations on the measuring cylinders to an accuracy of 0.5-percent, so I think you can ignore that small amount that might be left in solution.

E4ODnut posted 06-03-2011 10:02 PM ET (US)     Profile for E4ODnut  Send Email to E4ODnut     
I'm not a chemist either, which is why I found my results somewhat puzzling. Here's what I did with the same batch of our local pump gas using a good quality 100 ml glass graduated cylinder. I was careful to measure accurately, and keep the cylinders corked to eliminate any possible evaporation.

For a Fuel-Water mix of 90/10 the difference was 5 ml (5.6%). The sample decreased in volume by 2 ml.

For a Fuel-Water mix of 75/25 the difference was 5 ml (6.7)%. The sample decreased in volume by 0.75 ml.

For a Fuel-Water mix of 50/50 the difference was 4 ml (8)%. The sample decreased in volume by 4 ml.

For a Fuel-Water mix of 25/75 the difference was 1.5 ml (6)%. The sample decreased in volume by 1 ml.

I did them several times and the results were repeatable, give or take about 0.5 ml. It's hard to estimate values that are less than 1 ml.

I found the reduction in total volume interesting too. I did find that the 50/50 mix tended to stabilize within about 15 minutes, but the others seemed to take several hours to come to a final decision.

So, is a 2% difference probably within the margin of error? Could be, but I do wonder.

Do you know what ratio the commercial testers use?

jimh posted 06-05-2011 09:18 AM ET (US)     Profile for jimh  Send Email to jimh     
Thanks for the test data. My non-scientific observations:

The test which seems the most reasonable to me is the case where the fuel-water ratio was 75:25. I like it because it seemed to produce the least change in the overall volume of the solution. Also, the result you obtained from that test is about the average of all the tests.

It looks like your local gasoline retailer is selling blended ethanol-gasoline fuel with an ethanol content of about six to seven percent. This is encouraging, as ethanol in that concentration can usually be tolerated by most engines without special modifications being required.

I can offer a suggestion for further research in this method. Find a source of pure gasoline. Test this gasoline a bit to see if it does appear to be without any ethanol. If the pure gasoline passes the purity test, then intentionally dilute the gasoline with alcohol. It may be hard to find pure alcohol, however you can usually find rubbing alcohol sold in a 70-30 solution with water. Then you could dope your pure gasoline with some known amounts of alcohol, and create your own test fuels with various concentration of alcohol. This test fuel could then be tested by the several methods to compare the results with the known concentration of alcohol in the test fuel.

E4ODnut posted 06-05-2011 10:27 AM ET (US)     Profile for E4ODnut  Send Email to E4ODnut     
I did a bit more testing yesterday, mainly to compare the time it took for results to stabilize comparing the 75/25 mix and the 50/50 mix. As I mentioned, the 50/50 seemed to be quite stable within about 10 minutes or so. 75/25 seemed to take several hours, better if left overnight. A couple of hours into the test I thought, perhaps I should be shaking things up a bit, so I'd give the samples a good shake. Instant results in that there was a change to the 75/25. 50/50 was pretty well set some time ago. Eventually the results yielded the same calculated percentage.

So, this is what I've learned so far.

First of all, it's very important to measure accurately (kind of goes without saying).

Second, it is important to pre-measure the fuel and pre- measure the water. If you just put one in the cylinder first, then add the second to the 100 ml mark, unless you are very very fast, some of the methanol will already be absorbed into the water which will affect your accuracy.

I'll do some more testing to see what the shortest time I can get the 75/25 mix to stabilize if I shake things up regularly.

E4ODnut posted 06-08-2011 04:59 PM ET (US)     Profile for E4ODnut  Send Email to E4ODnut     
It looks like if you shake things up a bit the results match.

I tried shaking the solutions every couple of minutes. The 50/50 was stable within 5 minutes or less, the 75/25 took about 12 minutes or so. The calculated percentages were the same, as close as I could measure.

So it looks to me that you can use whatever ratio you like and get the same results. The downside to 75/25 is that it takes a bit longer. The potential upside is that the difference is going to be larger for a given methanol content. This difference is easier to read on the cylinder and the multiplication factor is less, so it should give you a better resolution.

Thanks again to Jim for the original article.

Stevebaz posted 06-08-2011 06:49 PM ET (US)     Profile for Stevebaz  Send Email to Stevebaz     
So does this mean when the time comes and we are fed up with the whole alcohol mess we build a cracking tower and phase seperate the crap from our gas and dump the rest and keep the best. Since water and alcohol evaporate there is no hazard waste. You can probably reuse the water that isnt tied to the alcohol. It just costs us more but is probably cheaper than repairs that the ethanol causes.
E4ODnut posted 06-09-2011 01:52 AM ET (US)     Profile for E4ODnut  Send Email to E4ODnut     
Well, I hadn't thought that far in to the future, but it sounds logical to me. Even with the best of intentions, I do wonder if we really are progressing.

jimh posted 06-09-2011 08:10 AM ET (US)     Profile for jimh  Send Email to jimh     
With a fuel of blended gasoline and ethanol, you generally do not want to remove the ethanol from the gasoline because the octane of the gasoline is typically too low. The ethanol is an octane booster.

This article is focused on a testing method. If you wish to discuss ethanol fuels in general, please start a separate discussion.

tjxtreme posted 06-12-2011 05:01 PM ET (US)     Profile for tjxtreme    
[Changed TOPIC. We are discussing a method for testing blended fuels for ethanol content. If you want to change the topic, please start a new thread. Thank you.--jimh]
tjxtreme posted 06-13-2011 03:04 AM ET (US)     Profile for tjxtreme    
Jim- Perhaps you misunderstood my question, I did not change the topic. I am inquiring about the method used to test for ethanol, and how the smaller vessel (graduated cylinder) would compare/contrast to a larger vessel (gas station storage tank). I see no difference between the two.
jimh posted 06-14-2011 11:17 PM ET (US)     Profile for jimh  Send Email to jimh     
Again, while not a chemist, I do not think the physical properties of materials change a great deal when the volume of the materials changes. A gallon of gasoline probably behaves about the same as 1,000-gallons of gasoline in terms of the solubility of water in solution with gasoline as a percentage of the volume.
tjxtreme posted 06-15-2011 02:40 AM ET (US)     Profile for tjxtreme    
Exactly, I agree. Therefore I don't think this method is valid for testing ethanol content. If it separated that easily then it would separate in the large tanks at the gas station. It makes sense for water, however. This scale issue is confirmed also by the TV show Flying Wild Alaska, where they often get water in their storage tanks and have to pull off the water portion.

PS I am sort of a chemist

jimh posted 06-15-2011 09:36 AM ET (US)     Profile for jimh  Send Email to jimh     
My understanding of the fuel business is that ethanol and gasoline are not blended together until the fuel truck arrives at a distribution depot. The gasoline and ethanol are blended as the fuel is put into a tank truck for delivery to a retailer. Blended fuel is only stored at the retailer's tank for a few days, or in the fuel tank of a consumer for a few weeks, typically.

Gasoline suppliers don't keep large amounts of blended fuel in storage, from what I know. I also read that blended fuels are not sent via pipelines due to concern that the blended fuel would scour the pipeline of decades of crud or pick up water in the pipeline.

Inasmuch as the testing method seems to be widely used, I have to think there is some validity to it. I don't see any argument that has been presented against the method other than to make an inference based on a conjecture.

jimh posted 06-20-2011 07:48 AM ET (US)     Profile for jimh  Send Email to jimh     
I came across a prior discussion on this method of alcohol content measurement. Here is the description of the method:

The presence of alcohol in gasoline can be determined by the “Water Extraction Method.” A graduated glass cylinder, usually 100 milliliters (ml), is used for the test. The procedure is as follows:

Place 100 ml of gasoline in a 100 ml stoppered glass
graduated cylinder. Add 10 ml of water into the cylinder and
shake thoroughly for one minute. Set aside for two minutes.
If no alcohol is present, the 10 ml of water will settle to the
bottom of the graduated cylinder. If alcohol is present the
alcohol will drop to the bottom, along with the water, increasing
the bottom layer to greater than 10 ml. The amount of
increase depends upon the amount of alcohol present.

(See Figure 4-3)

The graph in Figure 4-4 (page 24) assists in calculating
the approximate alcohol content when using the water extraction
test. Simply determine the volume of the lower phase
(bottom scale). The line that crosses that point on the graph
provides the volume of ethanol as listed on the left side of the

For instance, a reading of approximately 17 ml in the
lower phase indicates a presence of approximately 10%
alcohol. Although this test identifies the level of alcohol
present with a reasonable amount of accuracy, it does not
identify the type of alcohol. This presents a problem because
identification of the presence of 10 volume % alcohol would be
acceptable if the alcohol were ethanol. On the other hand, if
the alcohol were methanol, 10 volume % would be an illegal
blend and a blend not covered under vehicle warranty. Properly
formulated, a 10 volume % ethanol blend would not
typically result in driveability problems, whereas a 10 volume
% methanol blend would likely have an excessively high
vapor pressure and contain too much oxygen for proper
vehicle operation. Additionally, this test does not identify the
presence of ethers such as MTBE. More importantly, this test
gives no indication of the fuels volatility, octane, or other

The article was originally posted on the website of

I have preserved the graph at

Note that the total volume is 110-mL. The chart appears to have some sort of compensation, as the percentage of alcohol is not one-for-one with the volume change.

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