Honda 1998 Civic Sedan Manual page 150

Engine Oil
The oil container may also display
the API Certification mark. Make
sure it says "For Gasoline Engines."
API CERTIFICATION MARK
Maintenance
The SAE numbers tell you the oil's
viscosity or weight. Select the oil for
your vehicle 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 20°F(—7°C).
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, 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 vehicle's performance
or longevity. It only increases the
cost of operating your vehicle.