I have an original TEA-20 Reg number PRF 801 petrol chassis 55935 – first registered 21 Sept 1948. I have been running it on a mixture of Avgas and unleaded petrol is this ok? I have been told I should be running it on unleaded and “paraffin”.
I am not sure how similar our fuels here in the states are as compared to those in your area. There are three concerns we have regarding the use of regular unleaded gasoline available here.
The first is the absence of lead. It was originally added as a valve lubricant and antiknock agent. There are readily available lead substitute additives which can be added to gasoline and I recommend their use. I use them in the fuel in my own older tractor engines. I use a product sold under the CD2 brand label. As I recall it takes approximately 3 to 5 ounces of the additive for each 5 gallons of gasoline or petrol as you call it.
I believe the “paraffin”, which I believe is what we call kerosene, being suggested is meant to provide some of the lubrication properties that the lead substitute additives supply. If you can locate one of the lead substitute products I mentioned I believe it would be superior to “paraffin”. You could use one of the lead substitute additives with either Av gas or regular gasoline. To be honest, I don’t know if your gasoline or petrol contains alcohol or if it still contains lead.
The second is the addition of ethanol alcohol to our gasoline. This is a government requirement intended to promote the use of sustainable resources for fuel. Alcohol in any form has an affinity for water and fuel that has alcohol in it will absorb water from the atmosphere. Water tends to corrode fuel system components and the result is often rust in the bottom of cast iron carburetor bowls or the formation of other oxides on alloy components. Fuel with alcohol additives left in fuel tanks and carburetors usually result in corrosion so the best practice is to avoid leaving these fuels standing in fuel tanks and fuel systems for extended periods of time. Many collectors drain their fuel systems when their tractors will not be used for extended periods.
The third is the overall quality of the gasoline products available today. In an effort to reduce costs, lesser grades of crude oil are being refined and techniques which maximize production often decrease fuel quality. Aviation gas or av gas as you call it, is a good alternative to regular automotive pump gas and I know many people who use it in their tractors because it is cleaner, and free of alcohol. Most of these same people do add a lead substitute additive to it for additional valve lubrication. Another good substitute for unleaded regular gasoline with ethanol is something they sell here in the summer months only, alcohol free premium unleaded. That and premium unleaded are the fuels specified by 2 cycle engine manufacturers like Stihl.
Because these fuels have either no ethanol or less ethanol they are better for the fuel systems of 2 cycle engines because they do not cause corrosion like ethanol additive fuel does. These small engines are usually made of light weight alloy parts. Many small engine dealers here are also selling premium unleaded alcohol free gasoline in sealed containers as a premium fuel for engines. The price is usually at least double the price per gallon of pump gas or gas purchased at a filling station but they claim it is a fuel you can leave in a stored engine for an extended period of time.
If an engine is equipped with Stellite faced valves and valve seats, using unleaded gasoline should not damage the valves or seats. Stellite faced valves and valve seats were a replacement parts option for the TO-20 available from Ferguson and Massey Ferguson. Stellite faced exhaust valves were standard equipment on the TO-30. Newer engines made to run on unleaded gasoline are usually equipped with Stellite faced valves and valve seats. You might consider posing your question to the Friends of Ferguson Heritage in the UK.