Prizm L4-108 1.8L DOHC VIN 8 MFI (1995)
Spark Plug: Description and Operation
NORMAL SERVICE
Normal service is considered to be a mixture of idling, slow-speed and high-speed driving. Occasional or intermittent highway driving is needed
for good spark plug performance. The higher combustion temperature generated during highway driving burns away any deposits of carbon or
oxides that build up from frequent idling or continuous stop-and-go driving.
SPARK PLUG HEAT RANGES
Spark plugs must operate within certain temperature limits if they are to provide the performance and service life expected. The spark plug
selected for an engine is based on the normal service for which the engine was designed and may not perform satisfactorily under other than
normal operating conditions. For almost exclusive city driving, a spark plug one step higher in the heat range might deliver longer service life than
the spark plug recommended. Conversely, a spark plug one step colder will perform better for heavy loads or continual high-speed driving.
SPARK PLUG SELECTION
There are three rules to follow when selecting spark plugs for an engine in good condition:
1. Select a spark plug with the specified heat range.
2. If spark plug overheating occurs, select a spark plug that is one heat range lower than the specified heat range.
3. If fouling is a problem, select a spark plug that is one heat range higher than the specified heat range.