Honda 1997 Civic Sedan Online Reference Owner's Manual page 128

The oil container may also display
the API Certification mark. Make
sure it says "For Gasoline Engines.'
API CERTIFICATION MARK
The SAE numbers tell you the oil's
viscosity or weight. Select the oil for
your car according to this chart.
Ambient Temperature
An oil with a viscosity of 5W-30 is
preferred for improved fuel economy
and year-round protection in your
Honda. You may use a 10W-30 oil if
the temperature in your area never
goes below 2 0 ° F ( - 7 ° C ) .
Engine Oil
Synthetic Oil
You may use a synthetic motor oil if
it meets the same requirements
given for conventional motor oil;
energy conserving, a service
classification of SJ or SH, and the
proper weight as shown on the chart.
When using synthetic oil, you must
follow the oil and filter change
intervals given in the maintenance
schedule.
Additives
Your Honda does not need any oil
additives. Purchasing additives for
the engine or transmission will not
increase your car's performance or
longevity. It only increases the cost
of operating your car.
Maintenance