[Wild Bill]

True, the lead was introduced into the gas in the '20s
In the 1920s, antiknock compounds were introduced by Migley and Boyd, specifically tetraethyl lead (TEL). This innovation started a cycle of improvements in fuel efficiency that coincided with the large-scale development of oil refining to provide more products in the boiling range of gasolines.

I still doubt that Kohler engineers in the late 1950s/early 1960s were designing engines to burn fuel that had not been available, (or at a VERY minimum, widely used) for 30+ years. Did they have a crystal ball or something? How would they know that 10 to 15 years after they would design an engine for OPE usage, that the US Government would decide to start phasing out the fuel that was common for it's day, and mandate a fuel with a different chemical composition............

The lead was introduced for a reason, and that same reason is why other products are still introduced into the gasoline we use today, not to mention all of the other multitude of chemicals added to appease the feds.

Will the old Kohlers run on unleaded...apparently so. As does a whole bunch of other equipment-trucks-tractors-L&G equipment, etc, etc, that were designed and built long before 1973. PLUS just because the unleaded was being phased in beginning in 1973, does not mean that it was an instant 'flip' to it's use. The transition went into the 1980s. So to say that these old engines were puposely designed to burn a fuel that was not in use at the time, is asinine.