Testing the ethanol content of fuel

I recently picked up an E30 tune for my car from EQT.

Before I can calculate how much E85 and 91oct to mix together to get E30 I need to know what each of their respective ethanol content is. E85 is typically rated UP TO E85 but may be and commonly is lower. I have been told my area E85 stations are closer to E79 but some other areas are as low as E54. Most (but not all) normal gas also has UP TO E10 worth of ethanol in it.

Testing this is actually easier than you might think. Kits are cheap off amazon, this is the one I picked up. Per the directions for the kit:

  1. Fill with water to the “Water Fill Line”.
  2. Fill with the Gasoline or Alcohol to the top edge of the bottle.
  3. Reapply Cap and Firmly tighten – To avoid any leaking liquid.
  4. Shake until contents are fully blended (or suspended).
  5. Rest on a flat surface and let the contents (Gasoline, Alcohol and Water) settle out of suspension.
  6. Any Alcohol/Water present will appear above the “Water Fill Line” and under the Gasoline that is present above it.
  7. The volume present above the “Water Fill Line” will represent the total percentage of Alcohol/Water present in the Gasoline or Alcohol that was tested.
  8. When test is complete simply pour out contents & allow air dry. When dry, reapply cap and the tester is ready to be used again.

I am going to try and test a few stations around me over time. I will be testing both the E85 and 91oct so I can accurately calculate the mixture I need. There are lots of phone apps and websites like this one that can help you calculate your fuel mixture. One thing to be careful of is the existing ethanol content in your tank when calculating. This is why an ethanol fuel gauge is suggested like the ones from Fuel-it or Innovate Motorsports.

This site has been pretty good for finding E85 in my area: https://afdc.energy.gov/fuels/ethanol_locations.html#/find/nearest?fuel=E85

Here is a Google sheet shared with the results of the testing: https://docs.google.com/spreadsheets/d/1Z0nzHev42ZPxQAOpLk_9AxidcpdH3ebzQPw_QU61840