For the Mirage, I use the cheapest crap readily available. If I have time to shop around, I look through various fuel stations for a recent fuel spill and sop up all that I can and squeegee it into the tank.
In theory (not in practice), I bet I could plumb a hose from my Scamp's exhaust pipe to the intake of the Mirage ... block off the fuel lines of the Mirage, and the car would run off the exhaust of the Scamp idling exhaust! 5.9L of rich exhaust feeding a 1.2L. Should orta work. I'd just have to strap the Scamp to the roof of the Mirage.
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View my fuel log 2020 Mirage ES 1.2 manual: 42.5 mpg (US) ... 18.1 km/L ... 5.5 L/100 km ... 51.0 mpg (Imp)