The Ethanol Issue

Gasoline containing ethanol has become the new standard for fuel, and it presents a new set of challenges and work for classic car owners. You’ve got to be vigilant now to ensure a good running engine and prevent damage to your cherished car.

What’s the problem, you ask?

Ethanol, made from corn or grain, is added to gasoline to oxygenate it, replacing the older additive, MTBE. Names for gasoline mixed with ethanol include E10, gasohol, corn fuel, alcohol fuel, and reformulated or renewable fuel.

The key problem is that ethanol absorbs water from the atmosphere. In fact, fuel with 10 percent ethanol absorbs up to 50 times more water than standard gasoline. Older gas tanks found in many classic cars vent to the atmosphere, increasing the likelihood that moisture will be absorbed into the gas tank at a rapid pace.

The end result of water in the fuel is phase separation. The fuel separates into two distinct layers: a thick layer of gasoline mixed with a little ethanol on top, and a thinner layer on the bottom consisting of water mixed with most of the ethanol. And it doesn’t take much water for this to happen—phase separation occurs in a gallon of 10 percent ethanol blend with just 3.8 teaspoons of water.

Fuel Phase Separation Problems

What happens to your car and it’s performance when water causes fuel phase separation?

Reduced fuel longevity: A gasoline/ethanol blend absorbs water until it triggers phase separation. The blend has a 90-day product life in a closed tank, but lasts just 30 to 45 days in a vented tank often found in classic cars. With 10 percent ethanol blends, owners are supposed to replace the fuel in vented tanks about once a month by driving or draining, taking into consideration the humidity in the atmosphere and temperatures.

Vented or Closed Fuel Tank?

Not sure whether your British car has a vented or closed fuel tank? You need to know this detail in order to have a feel for how long the gas in your tank will remain good.

A sure giveaway of a closed tank is the presence of a carbon canister, which was added for pollution control purposes along with the closed fuel tanks. It’s often located at the back of the engine compartment, on the passenger side. To verify what it looks like and the positioning in your car, look at the diagram of the engine compartment for your car model on the Moss website, Note that some aftermarket gas caps are vented, so they can render a closed system open to the atmosphere.

Lower fuel octane: The ethanol in a gasoline blend provides some of the octane rating. When phase separation occurs, the octane rating of the remaining fuel can drop by as much as three points.

Poor engine performance: The fuel pump could easily pick up a slug of the water/ethanol slurry at the bottom of the tank, interrupting the flow of gas to the engine. This will cause the engine to miss, run rough and possibly stall altogether.

Corrosion and rust: Water in the bottom of the fuel tank and inside the fuel lines will cause corrosion and rust, and the solvent properties of the ethanol will loosen that up, along with bits of sediment and deposits. The resulting debris floating in the fuel could clog fuel filters, fuel lines and carburetor float valves.

Specific Parts Affected by Ethanol

Fuel tank: Ethanol could dislodge sediment and deposits in older gas tanks and fuel lines. Loose debris in the fuel could clog the fuel filter, or cause engine flooding if the carburetor float valve sticks.

Fuel pump: Rubber diaphragms inside the fuel pump may have problems with ethanol exposure.

Carburetor float valve: Float valve needles on early cars were brass, and these were replaced with plastic needles or brass needles with Viton (a specific type of rubber) tips. Ethanol can cause the plastic needles to swell up and stick either open or shut, which causes either massive flooding or starves the carburetor for fuel. Some owners have resorted to shaving down the plastic needle to get it to ride smoothly and seat properly. Instead, you can install an all-brass needle and seat, or a Viton-tipped needle if available for your car model, which are not affected by lower levels of ethanol.

Carburetor floats: The Zenith-Stromberg floats found specifically/only in the TR4 and 4A made of foam covered with a skin may deteriorate when exposed to ethanol. Other plastic floats, like those used by SU, may also be affected.

Hoses: Ethanol could dry out or deteriorate rubber hoses.

Seals: Ethanol could shrink, swell or deteriorate seals, depending on the material.

Gaskets: Ethanol may deteriorate the rubber in rubber/cork composite gaskets. Fiber washers and gaskets are not affected.

Aluminum and aluminum alloy parts: Aluminum and alloys fare fine with 10 percent ethanol, but are damaged by 25 percent ethanol.

Avoiding Ethanol Problems

Run your engine on fresh fuel from a major supplier in a location with lots of traffic.

Add fuel stabilizers when you put gas in your car to lengthen the life span of the fuel.

Buy higher-octane gasoline to be certain your engine gets the minimum octane necessary for good performance.

Keep track of the dates you buy fuel, how much you bought, and how much is in the tank when left sitting for a period of time. Keep a log book for reference.

If you have a closed tank, make sure it is truly closed. Listen for a hiss of air escaping when you take the gas cap off after driving.

Test your gas tank periodically to see if water is accumulating or phase separation has occurred. Treat accordingly.

If you don’t have a fuel filter before the carburetor (many British cars only have a screen), consider installing one to catch loosened rust and sediments from the gas tank before it clogs engine components. Moss offers one with a glass bowl for at-a-glance inspection, yet it features a period-correct look (Fuel Pressure Regulator/Filter #377-435). Check your fuel filter often.

Consider adding a second fuel filter between the tank and the fuel pump to protect the fuel pump from damage from loose debris from the tank (Moss part #377-310).

Keep engine parts well lubricated to counteract the solvent effect of ethanol.

Regularly inspect all fuel system components, seals and connectors from the tank to the carburetor. Ensure there are no leaks and the system is in good shape.


Full or Empty?

Trying to decide whether you should keep your fuel tank completely full or near empty? The answer isn’t clear. It all depends on how you’re using your car, the humidity where you live, the type of tank found in your car, and your willingness to closely monitor the situation.

During the driving season:

Some British car owners keep very little fuel (treated with fuel stabilizer) in their tank, and when they take it out, they first stop at the gas station to put in about the amount of gas they think they will need. That way they are always running fresh gas, and they park it back in the garage with a small amount of treated fuel to minimize the amount of gas that could go bad and separate. But British fuel gauges are notoriously inaccurate, so you could run the risk of running out of gas on the way to the gas station.

Other owners keep the tank completely full, which means the surface of the fuel exposed to the humidity in the atmosphere is restricted to just the diameter of the fuel filler neck rather than the larger surface area inside the tank. Of course absorption of water by the ethanol is affected by whether the tank is vented or not, and by the humidity at that time of year. But considering the short life span for ethanol/gasoline blends, you’ll have to add fuel stabilizers and drive the car enough to regularly burn up the gas so your whole tank of fuel doesn’t go bad.

During the winter:

Whether you’re storing your car over the winter or driving it every once in a while in cold temperatures, your strategy for your fuel tank may be different at this time of year. If you leave a vented tank full, even with fuel stabilizers, you’ll have phase separation and water in two months. That means draining the tank every two months to eliminate the bad fuel and harmful water. If you leave it until spring, you could have to deal with the effects of rust and also still have to drain the tank.

If you’re lucky enough to have a closed tank, you may be able to get through the winter with fuel stabilizers, which gives the fuel a six-month life span. You could drive out of the garage come spring unscathed. To be sure, test the tank for the presence of water first, and emulsify or drain the tank contents if necessary.

If you leave your tank near empty with just a bit of treated fuel in the bottom during the winter, you won’t have much ethanol to absorb water into the tank or much gas to go bad. But the steel walls of a near-empty fuel tank will condense with the shifting cold-warm temperatures, creating more water in the tank and potentially rusting the sidewalls, as well as the floor of the tank where the water accumulates. This condensation would happen in both vented and closed empty tanks.


1. Use a fuel stabilizer when you put gas in your British car.

Most of us don’t drive our classic cars on a daily basis, so the short gasoline/ethanol life of 30 to 45 days in a vented tank, or 90 days in a closed tank, is a problem. In order to extend the life of your car’s fuel and delay the phase separation that will eventually occur, you can add a fuel stabilizer to your tank every time you put fuel into it if you’re not sure you’ll use the gas within the product life span.

220-360 E-Xtend Ethanol Gasoline Treatment (8 oz.)

E-Xtend doubles the fuel’s life to about 60 days in a vented tank, and about 180 days in a closed tank. It also contains antioxidants and de-gumming agents to fight sludge and prevent resin/gum deposits in the fuel tank. As a result, the fuel filter stays cleaner longer and the engine runs better.

For fuel with 10 percent ethanol, the ratio is one ounce of E-Xtend for every six gallons of fuel, so one 8-ounce bottle will treat 48 gallons of fuel. The long-neck bottle makes it easy to pour into the filler neck.

2. Test your tank periodically for water presence and phase separation.

When you’re not driving your car and putting fresh gas into the tank, or after the car has been sitting over the winter, you can test your tank to determine if water is present or if phase separation has occurred.

One test method is loosening the fuel tank’s drain plug and capturing a small sample of fuel from the bottom of the tank in a clear container for inspection. Since water collects at the bottom of the tank, you should be able to see the two layers if water is present—a pink layer of gasoline on the top, and a clear or white layer of water and ethanol on the bottom. It looks a lot like unmixed salad dressing. You can use a test kit on the drain sample if it appears mixed up.

If your tank construction allows a dipstick (a dowel or rod works well) to go from the filler neck all the way to the bottom of the tank, you can use a test kit for easier and more reliable results. (This test method won’t work on car models with a bent filler neck unless you can figure out a flexible dipstick that hits the tank bottom.)

220-362 Water Probe Indicator

Simply apply the Water Probe Indicator on the end of the dipstick; it turns red where there is water in the fuel tank. For example, if there’s a half-inch of water in the tank, the stick shows a half-inch of red.

3. Add an emulsifier to treat separated fuel layers.

If you find water in the tank and phase separation has occurred, you can add an emulsifier to the fuel to remix the gasoline, ethanol and water. (Note that if there’s an excessive amount of water, you may have to drain the contaminated fuel from the tank.)

220-355 E-Zorb Ethanol Gasoline Water Remover (16 oz.)

E-Zorb emulsifies the water/ethanol layer at the bottom of the gas tank created by fuel phase separation. The water and ethanol mixes back into the rest of the fuel in the tank. The water passes with the gasoline through the engine and is released as steam. The fuel regains the octane (up to three points) that was lost when most of the ethanol separated from the gasoline.

The ratio is one ounce of E-Zorb for 20 gallons of gasoline/ethanol. The one-pint (16 oz.) bottle will treat 320 gallons of fuel. You’ll have to agitate the fuel and emulsifier in the tank by rocking the car from side to side, and bouncing it up and down. Make sure your suspension can handle this!

By Moss Technical Services

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'The Ethanol Issue' has 1 comment

  1. January 24, 2020 @ 3:26 pm Peter Vander Meide

    This was a very helpful article. My 2003 Hyundai with 297,000 miles on it started to have engine missing problems. I have maintained it very well but couldn’t figure it out until I noticed that it would start to miss more when I got to the top of hills. This indicated water in the gas when the angle of the tank changed.


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