Modern Fuel in Old Cars

Many of you will surly recall the days in the mid-70s when unleaded gasoline first started to become widely available. At that time it was intended mainly for “new” cars with Catalytic Converters that were expensive to replace and would easily be damaged if exposed to good old “lead” or to be more specific, tetraethyl lead. Never mind the fact that it was highly toxic to living creatures, was actually proven to be abrasive to cylinder walls and rings not to mention that it tended foul spark plugs; we knew it to be “good” for our older engines. It was added to  the formulations by the gasoline companies for raising octane levels to allow higher compression by preventing knocking as well as avoiding recession of valve seats by providing a cushion or lubricating qualities.

Beginning in 1972, most manufactures added hardened valve seats and lowered compression rations in anticipation of coming emissions laws and unleaded fuel. For a while into the mid-80s or so, most gas stations offered both unleaded and leaded fuel. Of course the smaller nozzle size on the unleaded pump was designed to fit the smaller filler pipes on the new unleaded cars preventing leaded fuel from being used and toasting the converter. You could put unleaded fuel into an older vehicle if you wished but few did. Gradually however, the leaded fuel went the way of the dinosaur leaving unleaded as the only choice. This period was full of controversy which continues to this day regarding potential damage to non-hardened valve seats. In the spirit of rebellion, many owners of newer cars and light trucks had their catalytic converters hollowed out or replaced them with “temporary test pipes to verify the need for converter replacement only”. Also, plastic reducer adapters were readily available to allow the owner to pump leaded gas into the filler neck of a newer vehicle.  Once the big foot of the law and the economics of selling two types of gasoline gradually dominated, leaded fuel all but disappeared across the nation making lead additives, octane boosters and other substances very popular products for adding to gas tanks. They were dark days indeed for old car and truck folks or so it seemed at the time.

This brings us to the present day and the much bigger problem of what to do about ethanol and our old cars and trucks. Much has been written recently about the negative effects of ethanol in our gasoline, in fact an excellent and highly recommended article regarding Alcohol in Gasoline can be found on page 20 in the June 2010 issue of Skinned Knuckles. With real 100% gasoline no longer being available except in super expensive racing fuel form, the proliferation of “E-10” which can contain “up-to” 10% ethanol and the threat of “E-15” looming on the horizon; it looks as though Big Corn is going to have its way regardless of how strongly old vehicle enthusiasts feel against it. The advertised benefits of ethanol indicate that the exhaust emissions are less harmful to the environment than fossil fuel, it raises octane levels, it is from a renewable source, it is cheaper and more. None of this is beneficial to our old cars and trucks however.

My intent is not to “add fuel to the fire” (pun intended) by further discussing some of the more commonly known negative aspects of ethanol such as rubber and plastic degradation, ethanol dissolving long undisturbed deposits, corrosion problems as well as lowered fuel mileage, but to point out some serious issues regarding performance, drivability and life of our older engines. One issue particularly with winter storage and the increased probability of fuel system condensation brought on by temperature changes is what is known as “Phase Separation”. This is a problem resulting in the ethanol and water actually separating from the gasoline as it sits in your tank. Once Phase Separation occurs, the ethanol cannot be re-mixed with the gasoline and you have a layer of 100% lower octane gasoline, a layer of ethanol and below that, water all sitting in your gas tank.

My background is in mechanical design and I won’t pretend to be a chemistry professor but in a nutshell, here is what happens; the ethanol is hydroscopic which of course means that the ethanol and water have an affinity to one another. When condensation occurs, it is drawn into the ethanol portion of the fuel. When it becomes saturated and cannot hold any more water, the ethanol and water both separate from the fuel mixture and you have trouble. The percentage of ethanol in the fuel blend determines how much water can be absorbed before the separation occurs. The higher the ethanol content, the more water can be held in suspension. Reach the maximum and they both begin to separate out of the blended mixture into their own layers or phases. This can happen in as little as 90 days or less depending on conditions. One solution is to use up all the fuel and run the tank dry but that isn’t practical or even always possible. Another alternative is to keep the tank as full as possible and seal off the filler neck opening and carburetor throat with some plastic food wrap to minimize venting to the atmosphere but you need to remember to remove it before running the engine as older vehicles have vented gas caps and need to have air displace the fuel as it is used. An additional solution is to use a quality fuel preservative that is specifically formulated to prevent Phase Separation. There are several excellent products on the market intended for this purpose and one that I like to use is Eastwood Fuel Guard for Storage. 

There is a lesser known and infrequently mentioned issue which is the lower Stoichiometric Ratio of ethanol vs. gasoline. You likely have heard of the ideal air/fuel ratio of 14.7 to 1 for gasoline engines at sea level. This is the ideal Stoichiometric Ratio for the most complete and efficient combustion of gasoline and the ratio that all gasoline engine fuel systems are designed to deliver. Higher than that, toward 16 to 1 and the mixture is considered to be “lean”, lower than 14.7 to 1 and the mixture is “rich”. We are all familiar with having a choke partially closed on a cold engine to “richen” the mixture and the resulting sooty and strong smelling exhaust that results. The opposite lean condition will result in decreased performance, excess heat and detonation resulting in severe stress on engine components. This is where the old ethanol monster shows itself again unfortunately. A mixture of 10% ethanol will result in a Stoichiometric Ratio of about 14.0 or 14.1 to 1. Running constantly like this is a little too lean for a vintage engine to be happy. Of course a lesser ethanol percentage such as 7% will allow a slightly higher ratio but is still on the lean side.

What can you do? Well, drilling and enlarging or replacing the jets in a carburetor to provide a richer air/fuel mixture is the ideal way to solve it but that is certainly not always desirable. Another way around it although one that will most likely have an adverse effect on performance is to adjust your choke so that it is partially closed when the engine is warmed up and just always run it that way. An alternative is to add a slight restriction to the air intake or air cleaner. Just as a dirty air filter will cause a rich condition the downside is that these methods may hamper efficiency and performance.

There are also a number of good quality fuel testing kits on the market that are readily available for revealing the ethanol content of a fuel sample. These kits are quite simple to use and provide accurate results. They work by adding a small measured amount of fuel to a measured amount of water in a graduated cylinder, adding some dye, plugging the opening then shaking it vigorously; followed by a settling period. The ethanol will absorb the maximum amount of water; then the two will separate leaving a distinctive color band. By observing the width and position of the band in the graduated cylinder then comparing to a reference chart, you will have an accurate reading of the ethanol percentage in the fuel sample. I find it very helpful in determining the ethanol content of the fuel that I just filled my old cars with. As a side note, the average ethanol content in fuel samples purchased in eastern Pennsylvania this past fall have actually been in the 5% to 7% range. When I find a sample with lower ethanol content, I tend to return to that station although there is no real consistency and it will vary by delivery. You can also test a sample right there at the gas station before you fill up but it can raise some eyebrows when you stroll on up the store clerk and say “gimme 50 cents on pump 4”. I would like to offer a reminder to also properly dispose of the tested sample. I have found that a small turkey baster syringe works well for drawing off the actual gasoline (which will rise to the top and is now ethanol free) and dispensing it in my lawnmower tank.

I am continuing my research in this serious problem looking for solutions and finding ways to deal with it so we can all continue to enjoy our older cars and trucks without worry. As more information becomes available, I will provide updates in future columns. If you have any helpful solutions, suggestions or other positive input, feel free to share it with Eastwood and we will make it available to everyone.

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