Hatz Biplane Association

I have a converted O-290G on by CB-1. Typically use 87 autogas but now at an airport with only 100LL. I have heard you can run 100LL for a period of time then cycle back to autogas. I also so a Lycoming document once that addresses this but have not been able to find it when I need it now. Would appreciate opinions on this and reference to a specific document if known.

Mix 5 gal 100 octane with 20 gal premium unleaded. Perfect for low compression engines.

I thought perhaps some mox of the two would work. Appreciate the response.