No, the Lycoming doesn't need the lead. The lead is necessary to give the fuel certain needed characteristics - it's principally an octane booster. With older internal combustion engines the lead was helpful also to lubricate valve stems, but not with more modern engines having sodium-filled valves for instance (to transfer heat more readily and keep the valve stems cooler), etc. Metallurgy, design, and especially lubricants have all improved over the years.