Honda 1998 Prelude Owner's Manual page 189

Spark Plugs, Battery
Specifications:
NGK: PZFR6F-11
DENSO: PKJ20CR-L11
Spark Plug Gap:
0.043 in (1.1mm
Maintenance
Battery
Check the condition of your vehicle's
battery monthly. You should check
the color of the test indicator window,
and for corrosion on the terminals.
)
TEST INDICATOR WINDOW
Check the battery condition by
looking at the test indicator window
on the battery.
The label on the battery explains the
test indicator's colors.