In 1981 we ran some helicopters ,Astars, B206 and 500's (LTS 101 and C20Bs) on avgas for 5 days not knowing about it, our fuel drums were filled with avgas instead of jetB (still using jetB at the time) a couple of days later an AME noticed a white powder inside the exhaust of the Astar and phoned around trying to figure out what it was, he found out it was lead from the burned avgas doing it.
We stopped the operation for 2 days until new drums of JetB showed up and simply started working again. Nobody ever had any problems from it, at least on the job we were on.
JD