Does the Blower Increase Efficiency?

The answer depends on the furnace model type:

Counterflow Models

Counterflow models, which are equipped with a blower, have higher efficiency levels than the gravity-type models.

Gravity-Type Models

Adding a blower to a gravity-type model, where the blower is optional, will not increase the furnace's efficiency, but a blower will help warm a room more quickly.

Summary

While a blower won't boost efficiency on gravity models, it does improve heat distribution speed and provides significant efficiency gains when integrated into counterflow systems.