CITROËN C4 Handbook page 212

Practical information
The petrol or Diesel engine of your vehicle is
fitted with a catalytic converter, a device which
helps to reduce the level of harmful emissions
in the exhaust gases.
For petrol engines, the use of unleaded fuel
is compulsory.
The filler neck is narrower, admitting unleaded
petrol nozzles only.
If you have put in the wrong fuel for
your vehicle, you must have the tank
drained and refilled with the correct
fuel before you start the engine.
Fuel supply cut-off
Your vehicle is equipped with a safety device
which cuts off the fuel supply in the event of a
collision.
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Fuel used for petrol
engines
The petrol engines are compatible with
E10 bio-petrol (containing 10 % ethanol),
conforming to European standards EN 228
and EN 15376.
E85 type fuels (containing up to 85 % ethanol)
are reserved exclusively for vehicles marketed
for the use of this type of fuel (BioFlex
vehicles). The quality of the ethanol must
comply with European standard EN 15293.
Fuel used for Diesel
engines
The Diesel engines are compatible with
biofuels which conform to current and future
European standards (Diesel fuel which
complies with standard EN 590 mixed with
a biofuel which complies with standard
EN 14214) available at the pumps (containing
up to 7 % Fatty Acid Methyl Ester).
B30 biofuel can be used in certain Diesel
engines. However, this use, even occasional,
requires strict application of the special
servicing conditions. Contact a CITROËN
dealer or a qualified workshop.
The use of any other type of (bio)fuel
(vegetable or animal oils, pure or diluted,
domestic fuel...) is strictly prohibited (risk of
damage to the engine and fuel system).