Toyota Prius HSD User Manual download pdf (Page 13)

EPA Estimates

Purpose

The intent of the EPA efficiency values posted on each new vehicle window-sticker is only to

provide a basis for comparison, not an actual MPG expectation... as commonly believed.

Read the fine-print on this digital scan of an actual 2004 Prius window-sticker:

Don’t be misled by those large numbers. Real-World results vary significantly.

Ideal Conditions

Pay very close attention to the fact that the EPA tests are all performed under ideal conditions,

those that don't actually reflect real-world temperature or driving habits. Think of those values

reported as optimal, not realistic. You may be able to achieve them from occasionally, but not on

a routine basis.

Ranging Values

As mentioned on the window-sticker, there is a range of expected efficiency values. The large

numbers are really nothing but an average. In fact, the MPG isn't even constant for each vehicle.

Driving conditions, method of driving, and the influence of multiple drivers can all have a major

impact, causing fluctuation. Tank-to-tank measurements can vary quite a bit as a result, without

even taking into account the effect of seasonal cycles. None of these factors are represented when

the EPA tests are performed.

Unrealistic Speed

Back when the testing procedures were established way back in 1977, the speed limit on most

highways was only 55 MPH (88.5 km/h). That’s quite unrealistic for travel nowadays. Many

drivers cruise at speeds much faster. That causes a significant efficiency reduction, which is not

indicated on the window-sticker.

Unrealistic Climate

The "perfect summer day" climate portrayed during the testing is not what people actually drive

their vehicle in a great majority of the year. Winter extremes cause efficiency to drop significantly,

as do the Summer extremes. Factors such as temperature, wind, and moisture have a major

influence, causing the vehicle performance to be reduced in the form of lower MPG. To make

matters worse, the use of the Heater or A/C also contribute to lower MPG.

Prius User-Guide 13 of 54 Last Updated: 9/01/2007

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Toyota Prius HSD User Manual Page 13