is it the 4 stroke model or the 2 stroke ? if it is 4 stroke you need lead replacment fuel. 2 stroke is lead replacment fuel with 2 stroke oil mixed in
It is a Briggs and Stratton engine - an American engine. They normally only do petrol engines at that size, and it is most likely a 4-stroke, so its unleaded fuel straight from the pumps at the garage.
Briggs and Stratton did make a 2-stroke model once, but it never proved successful, so they stopped making it.
I guess it's all down to what age the machine is, and that will depend on whether it needs lead replacement fuel or not. I would hazard a guess that it won't need lead replacement petrol, because I borrowed an old Briggs and Stratton rotovator once - and it was very old, and that was 4-stroke with petrol straight from the pump - I did check with a local garden machinery dealer first, which is what I suggest you do before firing it up.