I restored a 1930 Buick and a 1938 Packard. Both required leaded regular gasoline back in their day.
The reason ............. Leaded gas provides a bit of lubrication. The valves were not hardened enough to fully support the new unleaded, hotter burning gasolines of today. With the original valves and seats, there was no lubrication to give the necessary protection they needed. So, that is why we add lead substitute to the older models. Now, if you have had your engine overhauled and the valves and seats were heat treated, the lead is not necessary. That is reason.
When I first had my 1930 Buick, an avid old car guy told me to add one gallon of good grade diesel fuel to a tank of gas. My tank was 20 gallons. Thus a 20:1 ratio was the formula. The tractors have an average 10 gallon tank. So one half gallon of diesel to 10 gallons of regular unleaded would be appropriate IF the engine still has the original valves and seats that are not heat treated and hardened. You may experience some smoke, irregular idling, sluggish starts and pre-fouling plugs with this cheaper method.
Personally, I do not use any additives in my '52 8-N and it runs just fine. But I do not use it more that two hours at a time just to grade my driveway. If you are mowing or plowing hours and hours at a time, I would strongly suggest the store-bought lead substitute additive to prevent serious valve problems down the road.
A few bucks of lead substitue could save you HUNDREDS of dollars down the trail.
Jus my dos centavos, Johnny
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