Aside from the price, gasoline hasn’t changed much in the last 100 years. But, with ethanol blends (i.e. corn fuel, alcohol fuel, renewable fuel, gasohol, E10, E85) becoming the new standard for fuel around the world, classic car owners are having more issues than ever before.

You see, ethanol absorbs water at a much higher rate than standard gasoline. And the gas tanks on many classic cars vent to the atmosphere, allowing moisture to get into the tank at an even faster rate. Once moisture gets in, it can cause huge problems… primarily, fuel phase separation. Phase separation is a process through which two layers form in the tank: a top layer of thick gasoline with very little ethanol, and a thinner bottom layer of water mixed with ethanol. Why is this a problem? Well…

1. Reduced fuel longevity: Ethanol blends generally have a 90-day product life in a closed gas tank, but a blend is only good for 30 to 45 days in a vented tank, like those found in many classic cars. This means that classic car owners need to replace the fuel in their vehicle about once a month.

2. Lower octane rating: Ethanol in a gasoline blend accounts for part of the fuel’s octane rating. With phase separation, the octane rating can drop by as much as three points, as water dilutes the ethanol.

3. Poor engine performance: Think about your fuel pump running that bottom layer of water and ethanol through the engine. Without a steady stream of gasoline, your engine can miss, run rough, or even stall.

4. Corrosion: Dare we say the dreaded ‘R’ word? RUST! Water in the bottom of the gas tank and in your fuel lines will lead to corrosion and rust. And ethanol actually acts as a solvent… so bits of that rust will loosen up and eventually work their way into (and potentially clog) your fuel filter, fuel lines, and carburetor float valves.

So what’s a classic car owner to do?

Fuel stabilizers are a good start, especially if you’re not sure that you’ll be able to use a full tank of gas in a month. Adding a fuel stabilizer to the tank when you fill up will delay phase separation, and can almost double the product life of an ethanol fuel.

You can also test for phase separation in the tank. Just remove the gas tank’s drain plug and catch a small sample of the fuel in a clear container. If phase separation has occurred, you should be able to see the two layers: a pinkish gasoline layer on top, and a clear or white water/ethanol layer on bottom. If you see the separation, you can use an emulsifier to treat the separated layers (effectively re-mixing the gas, ethanol and water). But, keep in mind that if there is too much water in the tank, your best (and only) solution will be draining the tank completely.

Keep your fuel fresh and you’ll be ready to hit the road when the next Pomona Swap Meet & Classic Car Show rolls around on March 2nd!