Just done some rough calculations and an extra two mpg would be about 6.5% improvement. Fuel cost of E5 over E10 at same station around 7% more. Think I'll give it a go as I'm sure figures can be massaged further
Richard
2018 Roadster 3.7 1966 Land Rover S2a 88 2024 Royal Enfield Guerrilla 450 1945 Guzzi Airone