I use ordinary unleaded. There are advantages in not using any fuel containing ethanol, because it might shorten the life of some elastomers in the fuel system.
My old 1963 Briggs had a label on it saying 'Use only standard petrol', which was fitted by Alroh in response to Briggs saying use only standard-grade gasoline. The advice made sense in the US, where it was the practice to produce super-grade petrol by adding extra tetra-ethyl lead, and the lead tended to gum up the spark plug, exhaust valve and muffler. However it was pointless in Australia where the practice was to produce standard and super petrol in the refinery from different constituents, then add the same amount of TEL to each (more or less the maximum amount allowed by law.) The older Briggs engines have very low compression ratios and can run on very low-octane petrol. Not so sure about the current OHV engines, but standard unleaded (91 octane) will exceed their requirements.