Mileage? Break-in period?

[Kathryn]

I've just had my car for a short time, but I've been keeping an eye on my supposed gas mileage. I zeroed out the counter before I took a shopping trip 50 miles away, mostly highway driving with some in-town, and got 53 MPG, which I thought was pretty good, and in synch with what they claim the Prius gets on the highway. Since my return, I've done primarily in-town driving (which is supposed to get better mileage, n'est-ce pas?) and I noticed that the MPG calculation keeps going down: first to 51, now around 49, which means that my in-town driving after my road trip has worse mileage than my highway trip.

What gives? I'm a "coasting into gradual braking" type driver, so I thought I'd be good at regenerating the battery.

Is there any kind of break-in period with the car (I vaguely recall reading somewhere that you get better mileage after the first 1000 miles?)

[mdacmeis]

You've simply fallen into the infamous "your mileage may vary" zone. The key to high mileage in city type diving is being able to drive constant speeds for a significant portion of the distance traveled AND being able to get into electric only operation. I suspect since you are new to this, it may simply take some time to get accustomed to the situations where electric only mode is possible and then get a better understanding of how to "coax" the car into this mode. There are a number of threads which describe how to get into "stealth" mode to take advantage of the additional MPG. The basics are to accelerate to the desired speed, below 42 MPH, briskly, then slightly let up on the throttle to just barely case the vehicle to decelerate. This will generally quickly shut down the engine, which you can see on the info screen that displays the power scheme by noting that the engine path has gone away. Now you slightly increase the throttle to maintain your speed, and if all is well, you will notice the yellow arrow from the battery to the motor only. A mile or two in electric only mode over 10 miles of city driving has a huge impact on your average MPG.

Reality is some "city" type situations are just plain unfriendly to MPG and you simply have to realize that getting 40 MPG under these situations is better than the 15 or so your last vehicle was likely achieving.

[Marg]

I get the impression that people are having a easier time approaching the EPA's highway driving figures than the city driving figures.

How long is your average city trip? If your trips are short (i.e. 10 minutes or less), your mileage is going to suffer. The car is less efficient during its warm-up phases.

What kind of traffic conditions do you have? When I am in conditions where the car must stop frequently and accelerate quickly in order to keep pace with traffic, my mileage suffers. If there are few lights and relatively consistent speeds, then the statistics really improve.

In my city, there is a highway where cars travel around 110 kph. We have some roads called "parkways" where the views are lovely, the traffic lights are few and the cars travel between 60 and 75 kph. Then there are standard city streets where there are lots of lights, lots of traffic, and the cars travel between 40 and 50 kph.

I always get the best mileage results on the parkways.

[jamarimutt]

The 60 mpg EPA city estimate is unreal. In my experience (7000+ miles), mpgs in the usual city driving conditions will always be lower than the highway estimate (50 mpgs, I usually get 51-52). You do save gas when stopped (because the engine is off) and while driving in electric-only mode, but in due time the battery will lose capacity and the ICE will start just to charge it.

To repeat from the previous poster, reality is some "city" type situations are just plain unfriendly to MPG and you simply have to realize that getting 40 MPG under these situations is better than the 15 or so your last vehicle was likely achieving.

[efusco]

I agree that the "ciy" thing is pretty misleading. If by city one means accelerate to 35mph for one block then stop at a light, then accel to 45 for 2 blocks and stop, then go half a block accelerting before an idiot slows and turns without using a turn signal forcing you to brake hard since you couldn't anticpate only to accel again to have to stop in another 1.5 blocks for another light...then you'll NEVER see the 60mpg type of numbers.

OTOH, if your "city" driving is 45mph for 1-2 MILES at a time with predictible stops and slow downs where minimal braking is needed then you're going to start to see huge numbers even in excess of the EPA figures if you're using good technique, no A/C, and moderate acceleration.

[markhaney2004]

Kathryn

I have had a very similar experience to yours. When I first got my car, I drove 250ish miles on my way home from Houston. First tank - even second were above 50mpg. Then I suddenly started getting 47 to 49 consistently from tank 3-9. Now tanks 10-12 have all been 52mpg or better (54.5 is my high). I use synthetic oil (i don't think this makes that much of a diff) and my tire pressur is 42/40. I always use my air con, but at a reasonable setting (it's TX for god's sake).

The other mistake I made early on was accelerating too quickly. Now, around 20mph I always ease back a bit to get my mpg into the high 20s/30s while still accelerating (less quick than initially, but still ok - 20s/30s are always better than 15mpg).

Anyway, I thought I'd let you know it will get better and you will learn more about how the car drives everyday. It took me a long time to find a way to/from work that wasn't red lights every 10 feet and actually let me drive at slow speeds for significatn distances (35-40mph). This is key.

Good luck!

[Kathryn]

Thanks for the answers. It seems to me that "city" might literally mean "city" in this case, and not "podunksville of a small town" type driving. :wink:

I suppose I can look forward to the good mpg I'll get when I drive 3 hours on the highway to go to a meeting tomorrow (and 3 hours back).

[daniel]

The EPA "city" course is an unrealistic idealized standard course. If you drive that course you will probably get the EPA mileage. It's useful in that it puts every tested car on the same course. But unless you want to spend your life driving on the EPA treadmill, don't think too much about it.

The higher city than hwy numbers reflects the fact that the Prius gets its best mileage at well-below-highway speeds, but real city driving has too many stops and starts.

People expect better mileage on the highway, but don't understand the reason: Wind resistence increases exponentially with speed, but conventional cars are too inefficient at slow speeds to get the benefit of low resistance in the city. The Prius HSD is so efficient at slow speeds that mileage continues to improve as wind resistance drops. Thus it does better on the EPA city test. But real city driving has too many stops.

I think traffic jams had not yet been invented when the EPA tests were formulated, somewhere around the year 1913.

[DonDNH]

In my commute to work about 40 highway miles I average about 55 MPG; for the 4 or so city miles my average seems to drop down by 2 ro 3 MPGs.

The biggest hit to my mileage came earlier this week. Last Saturday I had my 5000 mile service. The tech set the tire pressure down to "recommended" against my orders. Driving to work on Monday yeilded only 49 MPG. Putting the pressure back to 42/40 brought the milage right back to normal.

[hdrygas]

So far I am doing very slightly better in the city than I did freeway driving home. I am beginning to get the induction of stealth mode. It is a real touch. In the interest of the "Olympic season" how about hybrid driving as a Olympic event for the next Olympiad. A three day event city, highway and mixed. Points for m.p.g. and time over the course. You would need handy caps for the various systems. I can see a professional circuit.