Toro 303447 Troubleshooting Manual page 14

There are some specific characteristics related to a four
cycle engine
Two complete revolutions of the crankshaft per cycle
results in a power impulse every other revolution.
These engines are more popular than 2 cycle
They do require more parts that 2 cycle.
Less exhaust emissions than 2 cycle.
Typical lubrication system restricts angle of operation due
to either splash lube from the sump, or pressure
lubricated, pulling oil from the sump.
They are also normally more durable than 2 cycle.