Thursday, April 19, 2012

DIY Ethanol Content Tester

          Anyone running E85..... As of June 2011 the minimun ethanol content of E85 was lowered to 51%. This means that a 51% ethanol content in E85 meets the regulations for E85, they can put E51 in the pumps and still call it E85. Everyone should be testing their mixes before filling up, making sure they have room in their tunes for this lower, or higher, depending on what mix your car was tuned on, ethanol content. Being tuned on E51 and then filling up with E85 will most likely leave you with hole in your wallet.... or your piston..... or both.

          In light of this information I decided to do a write up on how to make your own Ethanol Tester from stuff you can buy at most stores, and I'll explain how to use it. I wrote this little excel Ethanol Content file myself, so if there are any bugs, thats why. This is my first attempt at a DIY or a write up so if it sucks... well thats why again.

 What you need....

 1. Baby bottle (with graduations - lines that measure whats inside. Get one with the smallest graduations you can find, makes it easier to get readings later.)

2. Rubber Glove (could be optional)

3. Ethanol Content xlm file (100% optional, use this if you dont want to do the math) File is here on my Google Docs (you must download the file to use it)

NOTE: The xml file is picky about blank characters in the boxes, I plan to replace the XML in this write up with a excel file that can be ran from google docs, removing the need to download the file or have excel on your computer.

Update: The xml file had some issues so a stand alone app was made, look here for the download.

What you do..... 

 Step 1. 

(if not using the xlm file skip to step two and ignore the part where you are entering info into the program)

 Open the xlm file and be sure to click "Enable macros" if you are asked.

Next Click on the button to launch the Ethanol Content Analyzer Form

Step 2 

 Now you are ready to use your baby bottle. (If you have a baby at home, it may be a good idea to mark your bottle as do not Drink this had bad stuff in it.)

Take your empty Baby bottle and add water to one of the lines on the side (units will not matter here just be sure to be consistant with the units you choose)
Enter the number of oz or ml or whatever units you use into the water reading in the program. I used the UK fl-oz units from my bottle.

Step 3

 Add fuel up to another marked line on your bottle. (I over shot by a hair)
Enter this reading into the water + fuel reading in the program.

Step 4

 Put the rubber glove across the top of your bottle and screw your lid on. Shake the bottle up then place on a flat level surface and let sit for a few min.

Step 5

 The water and ethanol will mix and the "gas" will float on the top of the water. Look for this line of separation.
Note: Better picture at the bottom of blog.
(using white or colored paper behind the bottle can help you see the line)

Enter this reading into the Separation Reading in the program.

Step 6

 Now click the Calculate button and you will get a % Ethanol reading in the green box.

NOTE: I was using old e98 from last year that has been in my gas can all winter, so your bottle might look different than mine.
I also should have used the ml units as they are closer together and may have been a little easier to judge on the separation line.

 (or if you are not using the program now you get to do math. Take the quantity of the separation reading minus the water reading divided by the quantity of the water + fuel reading minus the water reading.)

Good luck with your Ethanol adventures. And feedback is always appreciated.


So I tested some fresh e85 from conrad and bischoff, 3-19-12, here in Idaho Falls ID.

Here is a much better picture showing the separation, and the program showing what it tests at.


  1. Hi, where can I download your E85 tester app from ? Awesome work btw

  2. The OS X app is no longer working, the windows app can be found here :

  3. Thanks mate, it runs a bit wierd on win8 but is still usable so thanks!

  4. You can also do the reverse to check the purity of methanol/ethanol?
    Measure out some meth, then measure some gas.

    Add the two, the separation should tell the volume of water in the methanol.