Opel Speedster Operation, Safety, Maintenance Manual page 84

Oils, coolant, brake fluid
Engine oils
We recommend using Opel engine oils with
the following qualities and viscosities:
ACEA A3-/B3- SAE OW-30
ACEA A3-/B3- SAE 5W-40
ACEA A3/B3- SAE 10W-40
When using commercially available engine
oils, as a matter of principle only those oils
that meet the minimum quality requirements
specified in the following table are
permissible.
Engines
Oils
ACEA- A3- or
ACEA- A3-/B3-
Petrol
Only the following viscosity classes are
permissible for petrol engines:
SAE 10 W-30 (or higher than 30) or
SAE 5 W-30 (or higher than 30) or
SAE O W-30 (or higher than 30).
The range of application of the oil is
dependent on the outside temperature, see
the viscosity chart on the next page.
Information on ACEA classifications
The Association des Constructeurs
Européens d'Automobiles classifies engine
oils according to their performance (quality).
Each category is given letters and numbers,
e.g. A3-98.
The letter indicates the field of application:
A = Petrol engines in passenger cars
B = Diesel engines in passenger cars
E = Diesel engines in trucks
The first number indicates the quality in
ascending numerical order.
The second number "98" signifies that the
ACEA classification is applicable as from
January 1998. Higher year numbers indicate
progressively refined oil classifications.