Why my mpg does not match promised values?

you can find good info on many gen 4 at fuelly.com, i think you are probably average. city driving, with a lot of stop and go eat up the mpg's. it is costly to keep moving a car from a stop up to speed.

the trouble with 5 miles is that you just get the engine warmed up, and then it's only a few miles to your destination, depending on temperature.

advertised mpg is not based on your particular drive. reset a trip meter, and take it on a 40 mile drive under varied conditions, and see what it shows for mpg.

what tyres pressure are you running?

what highway speed are you running?

 

A Prius does get its advertised MPG once it is warmed up. Short trips will always result in lower MPG. My 2016 Prius 3 has averaged 52 MPG (the computer says 54 MPG) over the two years and 21k miles I have owned it. My 2004 Prius averaged 46 MPG over 12 years and 288k miles.

JeffD

 

I drive where it is very flat*, so I see almost mathematically pure graphs of my MPG.
Each day it looks like this:

Now the red line may vary by wind direction and temperature, and the green line takes as little as 7 minutes when it is over 90 to 20 minutes below 30 to converge, but it always climbs to that red line then stays there for my 42 mile to 88 mile commute.

With a 5 mile commute, I suspect you never reach the red line. Is it possible for you to combine your trips into a longer single drive?

The EPA specifies the test is to be done in a fully warmed up car, so they have no 'first 5 miles' issue.

* US 49E in Eden, MS to US 61 in Walls, MS is 156 miles and gains 90 feet. (by comparison, the curvature of the earth could hide a 15,500 foot mountain at that distance)

 

Prius will get higher then the stated MPG. It all depends on how you drive it. I drive 25 to work and usual get 50 MPG to work on Gen 3. My co worker who drives with a heavy foot and drives the same miles and route get 38 MPG on her Gen 3 with less miles and newer. She thought I was lying when I first told how much higher MPG I was seeing.

 

I've done almost 30,000km on my 2016, averaged 4.1 l/100 - US56.8 MPG. Which is substantially less than the advertised figure of 3.4 l/100 combined (same l/100 for urban, 3.5 country). I do more motorway driving than around town 70%/29%.

This last week, I did shorter trips to dentist, pharmacy etc most days, and the daily average was higher (ie worse) like 4.8 -5.1. But next week, I've got a 100km commute on motorway, and it will typically average 3.5-3.7 on those trips. Interestingly, if the speed is steady at the speed limit, it will use more than if it's slower where it slows and regains speed as the traffic varies in speed. A lot has to do with how you drive - driving harder uses more fuel, like in any car.

I think RADAR Cruise, in some situations, may use a little more fuel - but I prefer to use it for the convenience.

I have had situations on an almost deserted road where it's beaten the advertised figure using hypermiling "pulse and glide" technique. But with traffic around, that's not normally possible - but you can use that technique on occasions if traffic is light.

I wouldn't panic - it takes time to get used to the car, and you'll probably find your technique improves.

There are some articles on hypermiling or "pulse & glide" technique which might help.

 

Yes - it's called carelessness by the pre-delivery guys. (Or - someone's gauge is wrong.)

 

you have to monitor tire pressure regularly. it is normal to lose a bit regularly, and they can change with ambient temperature.

 

Start by reading what the advertised information actually tells you. There's far more than just what the big values.

Expectations are a range that will fluctuate based on driving conditions. As others point out there are quite a number of influencing factors to be aware of.

You'll witness MPG go up & down as you become more observant. That data shown while you drive can really teach a lot about efficiency.

 

Displayed or calculated? Displayed, Toyota tends to BS, anywhere between 5 and 10 percent.

"Advertised" is a bit of a misnomer. All cars are tested under standardized condition, and it's rare to achieve that efficiency in day-to-day driving. For a sense of how your mpg compares to other, check out Fuelly.

ECO mode is mainly a simple remapping of the gas pedal travel, nothing special. Also, are you running the Air Conditioning all the time? That'll put a dent in mpg.

Partially because of the following:

If I can go into "Dutch Uncle" mode: you bought a car and you're surprised that the tire pressures are off? Also you're dismayed that you're not getting the rated mpg. I'm picturing you as being quite young, and this is your first car? You really should read up on basic car maintenance, also the impacts of short trips, higher speeds, tire pressures, on mpg.

 

Sound like a Prime, or even a PiP would have been the perfect car for you. You'd be getting well over 100 mpg.

 

Another factor might be cold weather, as that can hit MPG pretty hard. Your morning short trips when the temp is less than 45 will have poor MPG performance for sure. My guess is that you had a few cold mornings in March and early April?

 

It’s important to check and fill tires cold, the high side may have been in the sun, the cold side shade, but you also drove the car.
Most like 40lbs, the car asks for 36lbs, so a quality pressure gauge and a pump at home are ideal, parked out of the sun.
The tires lose 1 or 2 pounds a month, so a monthly trickle charge of the 12v battery and top up of air is considered regular maintenance.
With no pump, overfill at the pump by three or four pounds then the next morning,when cool in the shade, adjust the pressure to your desire.
A valve stem tool is nice, sometimes stems are loose, loose stems sink ships, err, lose air continuously.

 

I'll take a guess here. Was your Prius parked in the sun and and the right side tires facing it? A rule of thumb is to check and adjust tire pressures when all are at the same temperature.

 

As I hint, warmer temps will give you better MPG for the next 5 months, then depression hits. Pulse and Glide is an odd driving style where you gain speed then very lightly lose speed. Done very carefully, it can do better than steady state cruising. Done in traffic, it can make you and all other Prius drivers hated.

TPMS is a good failsafe, but as implemented on the Prius, is not ideal. (the wife's anti-Prius tells all 4 PSI reading on the dash)

If the car is new to you, you may wish to read the chapter on customization. Setting you doors to unlock exactly to make you feel safe and the windows to auto up and down as you like, etc. As an example, I park in a garage, so I disabled the delay in the head lights, if I parked on the street I might have wanted a longer delay so I could see all the way to my door. Lots of customizations possible, some you can change, some the dealer SHOULD do for free.

I used to give advice on who should and should not buy a Prius, but as a 2012 v owner, my experience is not up to date. Here is my post about the Gen 2 Prius considering a Prius | PriusChat