Answer (Ethanol):Today's gasoline includes up to 10 percent ethanol. In theory, all cars should be able to run on this mixture with no driveability problems. The problems start when the percentage of ethanol increases to 13 percent or more; such fuels are harmful to conventional engines and shouldn't be used in such applications. Recently, we encountered a vehicle that was actually vapor locking due to an ethanol content of 21 percent.
As individuals, there's no way we can regulate the ethanol content of the fuel at our local filling stations. But if you think you're having a problem with excessive ethanol content, there's a simple way to check the percentage of ethanol in your fuel.
Checking the Ethanol (Alcohol)Content of Your Fuel
1. Collect a fuel sample from your vehicle's fuel supply. Use a dry, clean container so your sample doesn't become contaminated
2. Pour 90 ml of your fuel sample into a 100ml graduated cylinder. Add 10 ml of water to the cylinder. Cover the top of the cylinder with your hand and shake.
3. Allow the fuel sample to settle for 10 to 15 minutes. The alcohol will combine with the water and separate from the fuel. The alcohol/water mixture will then settle to the bottom, since water is heavier than gasoline.
4. Note the line where the alcohol/water and fuel separate.
5. Now comes the calculation, using 100 ml as 100 percent. Subtract the 10 ml of water you added at the beginning of the test. The difference between the remaining alcohol/water and the gasoline is the percentage of alcohol in your fuel.
For example, let's say your water/alcohol line is at the 20ml mark. Subtract the 10 ml of water you added at the beginning, and you're left with 10 ml, for an alcohol content of 10 percent.
On vintage Corvettes, ethanol can loosen sludge, varnish, and dirt that have accumulated in the fuel tank. These contaminants can plug the fuel filter and cause an older tank to leak. Ethanol also absorbs moisture. The ethanol-water mixture in a car that isn't driven every day may separate from the gasoline and sink to the bottom of the fuel tank, where the fuel pickup is located. When the car is started, this mixture may clog the fuel lines or block the carburetor jets. It may also be incompatible with older cork or rubber compounds and some metals.
Got a question for our Tech Corner expert? Just jot it down on a paper towel or a lightly soiled shop rag and send it to us at VETTE Magazine, Attn: Tech Corner, 9036 Brittany Way, Tampa, FL 33619. Alternatively, you can submit your question via the Web, by emailing it to us at email@example.com. Be sure to put "Tech Corner" in the subject line.