yes, there is a break-in period for any new car.
from p. 144 of my old 2001 Prius owner's manual:
"BREAK-IN PERIOD
Drive gently and avoid high speeds.
Your vehicle does not need an elaborate break-in. But following a few simple
times for the firstr 1000km (600 miles) can add to the future economy and long life of your vehicle:
* Do not drive over 100 km/h (62 mph).
* Avoid full-throttle starts.
* Try to avoid hard stops during the first 300 km (200 miles)."
Mainly this is to allow for the engine to wear in, and so the brakes do not get uneven wear/glazing.
Some people have reported higher MPG after the break-in period, or up to ~3000 miles. Personally, I think it's more of the owner's getting to know how to drive their Prius more efficiently, rather than any real change in the Prius itself.
Obvious things to check out:
What are your tire pressures? At absolute minimum, they should be at 35 psi front, 33 psi rear (in the owner's manual). If you have the Bridgestone Potenza RE92 XL (50psi max) tires, you might even do better with your tire pressures up in the ~40psi range (with +2psi in front).
How long/far are your trips? Short trips kill mileage because the engine never gets out of its warmup stage. (this is a common culprit for low MPG.)
(Believe it or not, but sometimes taking the longer or seemingly more time consuming routes (backroad highways as opposed to gridlock major highways) will get you there in about the same time, but will lead you to higher MPG (~40MPH roads gives plenty of electric/regen time), and are often more scenic.)
What are the temperatures like in your area? Weather? (Cold temps will make your car warm up for a longer period.)
What are your roads like? Flat, small "hills," mountain terrains? Dirt, pothole salom, or well-paved?
What do you have your climate control system set to? If you have your fan direction set to the front windshield position, your engine will be running more often in weather over 32F because the front defogger runs the AC compressor (run by the engine) to dehumidify the air blown on the window. Change it to windshild/foot and you should be OK. Also, AC use will run the engine more (compressor is on the engine). Using the heater will siphon some heat from the engine/emissions system, which will cause the engine to run more often to warm everything back up.
how much stuff are you carrying in your car? any extra weight that might be unnecessary? carrying a roof rack or trunk hitch?
If you anticipate a long period of stop'n'slow, try to get as much regen as possible before approaching it. After so long of driving in pure electric, the engine will come back on to recharge the battery and really annoy you (and bring down your MPG).
For brake life and better MPG, anticipate your stops in general. Don't do the "hurry up to slow down" method of driving.
If you do mostly highway driving, try to stay to the speed limits. Like with any car, the faster you drive on the highway the lower your MPG will be, thanks to the physics of air resistance. low 60MPH seems best for the Prius.
If you're still having problems after trying out suggestions you receive, try getting a different Prius and do a comparison test over your same driving route. It's always possible that your car does have an issue, but there are others out there who have reported their MPG in the 30s too.
Since your car is new, I won't suggest the other MPG helper of an oil change and other checkup/tuneup suggestions that work on other cars.
Do remember, the EPA states (check your window sticker!) "City MPG: 52, Highway MPG: 45, Actual Mileage will vary with options, driving conditions, driving habits and vehicle's condition. Results reported to EPA indicate that the majority of vehicles with these estimates will achieve between 44 and 60 MPG in the city, and between 38 and 52 MPG on the highway."
BTW: The EPA tests don't exactly correlate to any real-world driving. (They even use a fudge figure to their results to try to make their ratings more real-world...)
taken from:
http://www.fueleconomy.gov/feg/info.shtml
How are fuel economy estimates obtained?
The fuel economy estimates are based on results of tests required by the U.S. Environmental Protection Agency (EPA). These tests are used to certify that vehicles meet the Federal emissions and fuel economy standards. Manufacturers test pre-production prototypes of the new vehicle models and submit the test results to EPA. . EPA re-tests about 10% of the tested vehicles to confirm manufacturer's results in EPA's lab. The vehicles are driven by a professional driver under controlled laboratory conditions, on an instrument similar to a treadmill. These procedures ensure that each vehicle is tested under identical conditions; therefore, the results can be compared with confidence.
There are two different fuel economy estimates for each vehicle in the Fuel Economy Guide, one for city driving and one for highway driving. To generate these two estimates, separate tests are used to represent typical everyday driving in a city and in a rural setting. Two kinds of engine starts are used: the cold start, which is similar to starting a car in the morning after it has been parked all night; and the hot start, similar to restarting a vehicle after it has been warmed up, driven, and stopped for a short time.
The test used to determine the city fuel economy estimate simulates an 11-mile, stop-and-go trip with an average speed of 20 miles per hour (mph). The trip takes 31 minutes and has 23 stops. About 18 percent of the time is spent idling, as in waiting at traffic lights or in rush hour traffic. The maximum speed is 56 mph. The engine is initially started after being parked overnight. Vehicles are tested at 68 F to 86 F ambient temperature.
The test to determine the highway fuel economy estimate represents a mixture of "non-city" driving. Segments corresponding to different kinds of rural roads and interstate highways are included. The test simulates a 10-mile trip and averages 48 mph. The maximum speed is 60 mph. The test is run with the engine warmed up and has little idling time and no stops (except at the end of the test).
NOTE: To make the numbers in the Fuel Economy Guide more useful for consumers, EPA adjusts these laboratory test results to account for the difference between controlled laboratory conditions and actual driving on the road. The laboratory fuel economy results are adjusted downward to arrive at the estimates in the Fuel Economy Guide and on the labels seen on new cars, light trucks, and vans. The city estimate is lowered by 10% and the highway estimate by 22% from the laboratory test results. Experience has proven that these adjustments make the mileage estimates in the Fuel Economy Guide correspond more closely to the actual fuel economy realized by the average driver.
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