Opel Astra 2004 Manuel D'utilisation page 34

Starting Characteristics
When starting in natural gas mode, the
starting time can be somewhat longer than
for a petrol-driven vehicle in a cold start
situation.
Fuels for running on natural gas
Any standard commercially available
natural gas can be used.
Fuel consumption
The fuel consumption figures were
obtained with reference fuel G20 (methane
content 99-100 mol %) under specified
driving conditions (70/220/EWG/EEC). If
natural gas of a different calorific value is
used, fuel consumption may differ from the
specified figures.
Optional equipment increases the kerb
weight and in some cases also the
permissible gross vehicle weight rating.
This in turn increases fuel consumption and
reduces the specified maximum speed of
the vehicle.
When the vehicle is new, there is increased
friction between the engine and
transmission components lasting for
several thousand kilometres. This increases
fuel consumption.
Refuelling
Petrol
See Owner's Manual: "Fuel Consumption,
Fuel, Refuelling" and page 42.
It is important to ensure that the petrol
tank is refilled after travelling in petrol
mode.
Natural gas
Care must be taken when handling
natural gas!
Before refuelling it is absolutely vital to
switch off the engine and any heating
systems with combustion chambers.
Natural gas is flammable and explosive.
Therefore avoid handling natural gas
near naked flames and doing anything
that would generate sparks. No
smoking! This also applies where
natural gas is noticeable only by its
characteristic odour.
If a smell of natural gas is present in the
vehicle itself, have the cause located
and rectified immediately by a garage
authorized for maintaining vehicles
powered by natural gas. We recommend
you to consult your Opel Partner.
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Natural gas consists of approx. 78 - 98 %
methane and is therefore also designated
"methane". In Germany, natural gas is
divided into two classifications depending
on the proportion of methane it contains.
The L-gas (Low) has a lower methane
content of approx. 80-87 % and H-gas
(High) has a higher methane proportion
of approx. 84 - 99 %.
For technical reasons, a vehicle propelled
by natural gas does not function with liquid
gas (and vice versa).
In contrast, a vehicle propelled by natural
gas can be operated with biogas, provided
that the biogas has the same methane
content as natural gas and has been
appropriately prepared chemically and
desulphurised.
Before recommissioning a vehicle which
has been out of service for a prolonged
period of time, check the test interval
schedule for the gas system (test sticker
near the tank filler neck).
If the test interval has passed, the vehicle
must not be filled with natural gas. Any
natural gas still in the natural gas tanks
may be used up.
For further information refer to the "Vehicle
recommissioning" section of the Owner's
Manual.