How to fuel old farm tractors designed to run on leaded gasoline
Sep. 2—In 1996 leaded gasoline was officially banned in the United States due to the Clean Air Act. Since then, other countries have followed in banning lead-containing gasoline, also called regular gasoline. Last month when the pumps ran dry of leaded gasoline in Algeria — the last country to ban it — that was the end of regular gas.
But it was not the end of vehicles and equipment designed to run on that fuel.
Older farm tractors and motorized farm implements were never meant to use unleaded gasoline. So there are few things that anyone purchasing a used tractor or older machine should know to keep it running well.
According to longtime tractor collector and restorer Dr. John Bouchard of Fort Kent, it's the engine's valves that required the leaded gasoline. Bouchard's collection currently has more than 40 vintage tractors he has restored.
"The issue with the lead is it lubricated the valve seats," Bouchard said. "That lubrication kept the seats from wearing out."
In a gas engine, it's the valves that let air or fuel into cylinders that allows internal combustion to take place in special chambers. That combustion is what creates the power to run the engine. Valve seats, according to Bouchard, are what provides the seal between the valve and the combustion chamber.
"If the valve seat does not seal well, you will lose combustion and won't have as much power," Bouchard said. "Your tractor will not perform well."
For older tractors that run on leaded gasoline, there are two options when it comes to using unleaded gas.
Bouchard said there are commercially available additives formulated specifically for engines that run on leaded gas. All you need to do is pour in the additive when you gas up your tractor each time. These additives are available at most automobile parts stores.
The other option is replacing any older valve seats.
"It was never really an issue with models like John Deere tractors," Bouchard said. "They were always designed with hardened valve seats."
Since those John Deere valve seats were made with a hardened metal, they did not wear as easily when unleaded gas was used. Other older models, Bouchard said, would have had original valve seats made with softer metal that was more susceptible to wear when used with unleaded gasoline. But he adds that time may have taken care of that issue.
"It would really be unusual for an older tractor to have never had a valve job at some point in its life," Bouchard said. "At some point a mechanic doing a valve replacement would have put in hardened seats."
Bouchard said you will know if your tractor does have valve seat issues if it does not want to start or run well. He noted depending on how often you use your tractor, unleaded gas may not be an issue, especially if it has the newer valve seats.
"For people using their old tractors as working farm tractors, you are probably going to want to use the additive on a regular basis," Bouchard said. "For people who are using their old tractors as more of a hobby it probably won't make a big difference if you don't use it."
