Back in the early days of tractors most were made to be able to run"tractor fuel" as it was referred to, now we call it kerosene. Some manufactuers referred to the as "all Fuel" Why? it was only a few cents a gallon and was cheaper than gasolline.
For the manufacturers to make a tractor run on kerosene they had to do a few thngs. Lower the compression to avoid knock, install two fuel tanks, a large one for kerosene and a small usually a gallon or so. Some even used water injection to prevent knock.
To run a tractor on Tractor fuel first you open the valve for gasoline to fill the carburetor, start the engine leave it warm up, close the gasoline valve and open the tractor fuel valve. Now you are ready to work.
To shut off the tractor you turned off the tractor fuel valve and allowed the engine to use the fuel in the carburetor. Next time you went to start the tractor you would be able to start it on gasoline, most would not cold start on kerosene. Even then if you shut it offon kerosene there was usually a drain on the carburetor bowl to drin the tractor fuel.
During the fifties most owners just filled the tractor fuel tank with gasoline and did not bother with the tractor fuel. Even most farmers converted the engine to gasoline only. Diesel was also being introduced and became popular about the same time.
Why use tractor fuel? price and sometimes was easier to get than gasoline.
Disadvantages of tractor fuel -- Less power than a strictly gasoline engine.
John Deere 60 - compression Drawbar horsepower all 321 ci
Gasoline 6 to 1 35.86
All Fuel 4.7 to1 29.17
LP Gas 7.3 to1 37.68
John Deere 70-- CI compression Drawbar horsepower
Gasoline 379.5 6.15 to1 42.24
All fuel 412.5 4.6 to 1 39.58
LP Gas 379.5 7.3 to 1 45.16
Diesel 375.6 16 to 1 45.09
Note cubic inch displacement for all fuel, gasoline, LP and diesel
Reference
www.tractordata.com