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External Loads
Hitch Racks & Roof Carriers cause aerodynamic drag. So, expect a MPG drop when you use one.
Engine Warm-Up
Short Trips are horribly inefficient for all vehicles. Prius is no exception; however, it’s far more
noticeable since the Multi-Display provides immediate feedback to actually show you the lower
MPG. The efficiency benefits of the system are not utilized until after warm-up is complete... that's
engine, emissions system, and tires. So try to run several errands at once to take advantage of an
already warmed up car.
PZEV (Partial Zero Emission Vehicle) is what Prius strives to remain whenever active, even during
warm-up. That means the catalytic-converter must be kept hot even if that requires using some gas
to do it. Fortunately, you still get better than average mileage, even if the engine doesn't shut off
right away.
5W-30 Oil
5W-30 oil is strongly recommended (real or synthetic).
If a service person puts 10W-30 in by mistake, you may complain since it will negatively impact
your MPG slightly and may affect performance in below freezing temperatures. The text on the
engine oil cap clearly states 5W-30 should be used.
Synthetic Oil
Owners have observed minor MPG improvements by switching to synthetic oil.
Plus, since it protects the engine better than real oil and makes extremely cold startups even easier,
switching from real oil should be a simple choice.
Oil Level
Too much oil can decrease MPG. Verify the level is never above the max mark on the dipstick.
Unfortunately, overfilling is a problem commonly overlooked. Oil change services routinely pump
oil from large barrels, rather than using quart-size bottles. That makes overfilling very easy to do.
Taking a moment afterward to check afterward is truly beneficial.
Measurement
The multi-display averages optimistically, so it will usually read about 1.4 MPG too high for most
owners. The "bladder effect" (caused by the bladder in the gas tank shrinking due to temperatures
below freezing), which is very noticeable in the Spring & Fall, causes the readout value and manual
calculations to vary greatly for individual measurements. Averaging several fill up amounts
documented at the gas station will provide the actual MPG you've been getting. For an example of
how to do this, refer to this webpage...
http://john1701a.com/prius/prius-data.htm
Break-In
For the first 200 Miles (322 km):
• avoid rapid deceleration (hard stops)
• avoid high speeds (more than 70 MPH, 113 km/h)
For the first 600 Miles (966 km):
• avoid rapid acceleration
• avoid racing (high RPM) the engine
After roughly 10,000 Miles (16,100 km):
• enjoy a MPG increase, from the moving parts having loosened
Even at 30,000 Miles (48,300 km):
• you may continue observe minor MPG increases as the car ages
Prius User-Guide 11 of 45 Last Updated: 2/07/2006