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Seasonal Cycles
Vehicle Types
Seasonal cycles affect all types of vehicles, not just hybrid. But with Prius, you are much more
aware of the MPG changes due to having a Multi-Display constantly informing you of efficiency
performance. With traditional vehicles, owners typically are not aware how much of an affect
climate has on their vehicle’s performance. They just assume MPG remains relatively constant
throughout the entire year. In reality, that isn’t even remotely correct. Large fluctuations are
perfectly normal.
Temperature
The difference between the warm & cold months is a significant change in MPG. In the winter…
The engine takes longer to warm-up, and the engine is needed to operate the heater. Both cause
more fuel to be consumed. The density of cold air is thicker, making it hard to push through. This
reduces efficiency. In the summer… Running the A/C to keep you cool requires electricity from
the battery-pack. That electricity is ultimately derived from the engine, which consumes fuel to
accomplish that. So, the more you use the A/C, the lower MPG will be.
These examples of real-world data (from
http://john1701a.com/prius/prius-data.htm ) clearly the
shows the effect of 4 separate Winters & Summers with a 2001 & 2004 Prius in Minnesota:
Traffic
It is common for people to forget how much traffic patterns change during the winter. Slippery
roads cause major delays, increasing driving time significantly. So even with the benefit of the
hybrid system, there is still a very real plenty for getting stuck in that traffic heavy traffic.
Heater
Heat to keep you warm in the winter comes from the engine. Hot coolant is circulated through the
heater-core as long is possible to continue heating the air. But eventually, it cools. At that point,
the engine must restart to warm the coolant again.
A/C
The A/C system in Prius is powered by an electric pump, not a pump powered by a belt connected
to the engine. That means in can run for a modest amount of time exclusively using only the
battery-pack, providing a significant efficiency benefit during the summer.
Prius User-Guide 14 of 45 Last Updated: 2/07/2006