Hi out there

Has any one tried to down rate there petrol as I have an Oliver 70 Crop Row and I know it should run on 70 Octain Gas, as the standard over here in the UK is 98 unleaded what can I do if anythiung and will the engine need retarding or can I down rate the fuel with something like Diesel or Parrafin. Anyone had any problems with running on modern fuels.

Regards

Richard (UK)