Ethanol fuel percentage
The share of ethanol in the fuel. This parameter exists on cars built for petrol and alcohol blends. The unit reads the share from a sensor or works it out from how the fuel trims behave, and changes the delivery: alcohol needs noticeably more fuel for the same air. If the Check lamp came on soon after refuelling and the trims went positive, this is where you start. On cars without alcohol support the parameter is either missing or sits at zero — which is normal, not a broken sensor. A sharp jump in the share between fill-ups on a car that cannot digest alcohol explains both the lost power and the higher fuel use at once.
What is normal
Close to zero for ordinary petrol. The figure only means something on cars built for alcohol blends.
How it feels behind the wheel
The same fault shows itself in different ways. Each sign below says what to look at in the live data.
How to see it
In CarScan: the Live data tab, «Start polling». The app asks the car several times per second, draws a graph and remembers the highest and lowest value of the trip.