Causes of LOW MPG Average?

Welcome to the club!
45mpg is not too bad. I think one question is what is the average length of the trips you are taking. My daily commute is only 8.5 miles each way (about 30min) which is not good for mpg--the ICE gets fully warmed up and is most efficient just about the time I arrive at work and shut off the car.
My MPG average tends to shoot way up when I take longer trips, even on the freeway.
Still, I could get 50mpg with short trips but I would have to work at it MUCH harder...via slow steady acceleration, pulse and glide, coasting down to stops, etc. I think if you keep working at it and experimenting you will get there.
Try perusing the posts in this forum 'cause there are lots of tips and theories on how to maximize your MGP. Good luck!

 

Evan's link above is possibly the best advice available for anyone concerned about their MPG. check it out and see how you do

and pff, how can i forget, WELCOME to the fourm! feel free to stick around, check out the features of the site (Danny has set up a fantastic set of resources here)- check out the "features" menu on the top right of the page and browse around a bit.

 

I'd suggest you check your car by forgetting tank mpg and trip mpg. Look at your steady state mpg at a fixed speed on level road over a few minutes after the car is fully warm and you are in stage 4.

Note the temperature and humidity too. Then plug into Wayne Brown's palm program if possible, or else look up some of the tables of mpg vs speed that have been listed here based on this simulator.

If you do this when there is minimal wind, you should get a good idea how you are doing.
Note that you may need over 12,000 miles on your car to get as good mpg as others here report.

After doing this, try a loop of about 30 miles or more on back roads where you can drive steady at speeds of 35 to 40 mph. Do not pulse and glide. Just drive steady. Find a route where you have minimal stops.
With AC off, you should be able to exceed 70 mpg. Reset your mpg when starting. It is far more useful on trips than measuring tankfuls which you can calculate anyway. After you do this and see great mpg hopefully over 70 mpg you can then work on things like pulse and glide to try to do better. Till you get the basics right trying the fancy stuff might just make things worse for you.

Now if you can get good mpg, just somewhere, you can then learn to see why it is bad in your normal driving. Could be trip lenghts, not getting into stage 4, AC use, really big mountains, too many stop signs or bad traffic, etc.

When you can be comfortable turn off the ac and open windows. Every time I've tested, mpg has been better with AC off in temps up to 85 degrees. If you drive 80 mph maybe AC is better than opening windows but then you won't get great mpg anyways.

Finally remember brakes are for emergencies. If you use them to stop fast or to stop every mile or two your good mpg will be gone.

 

<div class='quotetop'>QUOTE(galaxee @ Jun 26 2006, 07:29 PM) [snapback]277052[/snapback]</div>

Ditto
I had the same concern on my first tank and posted much the same question. That link explains a LOT!

I drive short trips - 5 miles each way to/from work. I'm half-way through my 4th tank of gas; first tank averaged 43 while I "learned" to coast as much as possible to slow down, anticpate the lights on my daily route, etc. It was easy to learn by just glancing at the 'consumption" screen and noticing the 'instantaneous' reading - example - there's a half mile stretch of road between two stop lights, and the second light says 'no turn on red'. It's a 'back way' with a 30 MPH speed limit. Often there's no one near me on that stretch of road. If I keep my foot on the accelerator to maintain a speed of 30, I ALWAYS have to stop for that red light. If, on the other hand, there's no one behind me, I'll 'coast' and perhaps tap the aceelerator when I slow down to 25, unless I'm very close to that stop light - I've let it drop down to 15 mph and still have to stop at that light. I then turn right and go through a small town for maybe 1.5 miles, where the speed limit's 25 or 30 - I rarely try to push myself up to 30, because shortly after the change in speed limit from 25 to 30, the road dips down for a bit - the car will get up to 30 without my stepping on the accelerator.

So my next couple of tanks were about 48 mpg, and the fourth tank looks like it's heading the same way, and I'm not likely to see much of an improvement until I happen to take one or more 'long' trips on a tank of gas, where 'long' means driving for 45-60 minutes instead of the typical 15 to 20 I drive on my commutes and the even shorter times for my 'errands'.

Several people have said they see an increase in MPG around 3000-5000miles, and some say that's because the tires are now 'broken in'.

Good luck with your mileage. I'm thrilled to be getting at least twice the MPG as my old car! So this is my wisdom after 10 weeks of ownership <g>

 

<div class='quotetop'>QUOTE(tomdeimos @ Jun 26 2006, 07:41 PM) [snapback]277058[/snapback]</div>

This is a great suggestion. I've only put about 500 miles on my new '06 and have averaged a sad 40.2 MPG so far. I also have an '02 Prius and I've driven it since Oct 2001 and have a lifetime average of 44 MPG on that vehicle. So I'm not a newbie to driving the Prius for good mileage. This time of year my '02 gets about 48 MPG with the same kind of driving I've been doing in the '06. Theoretically the '06 should get better mileage than my '02 but so far I wonder if there is something not quite right with the car. It's definitely not the A/C, since I sweated it out for about 100 miles without using A/C and saw only a miniscule improvement.

Like the topic starter of this post, I notice my '06 starting the engine when it really seems like it shouldn't. For example, going down a hill with the foot completely off the accelerator pedal at a speed of 36 MPH, and the engine starts! The battery icon shows 4 bars and the A/C is off, so I can see no reason to start the engine when it was just running on the way up the hill and shut off when I first took my foot off the gas.

One other thing I notice is that the starting and stopping of the engine is far more noticeable in the '06 than in my '02. I can feel a small but distinct "bump" in the car acceleration most of the time when the engine starts or stops. My '02 is much smoother in this regard, it's relatively rare that I feel its engine start/stop.

 

<div class='quotetop'>QUOTE(Hutchings @ Jun 26 2006, 04:40 PM) [snapback]277057[/snapback]</div>

Your short outings are your biggest problem not achieving higher mpg. You need to drive at least 30 minutes to make up for the first five minutes being low due to warming up. I have to admit that I try to have my wife drive her car if we are going to do a short trip. She thinks I am a bit of obsessed, but she's getting over it. :lol:

 

Stephen,

Are you actually pressing the button on the MFD to reset the MPG display?

Although I have seen it written that it resets automatically after refueling, for me it seems to be that the distance reading resets to zero but the MPG figure does not unless I actually press the RESET soft button on the display.

If you didn't reset it then what you have displayed is the MPG figure since you bought the car. That figure will change very slowly over time.

After a reset the MPG figure changes very rapidly - go up a small hill and it will plummet, coast a bit and it will rise to a very high figure.

kevin

 

<div class='quotetop'>QUOTE(kevin17 @ Jun 26 2006, 11:06 PM) [snapback]277160[/snapback]</div>

Bingo. I'll bet that's your problem! (As mentioned, trip length is also a major factor I've found)

 

<div class='quotetop'>QUOTE(Hutchings @ Jun 26 2006, 07:40 PM) [snapback]277057[/snapback]</div>

There's your answer. The shorter your trips are, the lower the MPG you will get. The longer your trips are, the higher the MPG you will get.

This is all because of the first 5 minutes of driving when the Prius runs less efficiently during its warm up cycle.

You have probably noticed on the Consumption screen that the first 5 minute bar on the graph is usually always between 25 and 35 MPG. Then the next bars are probably much higher, in the 45 to 60 MPG range. It's that first 5 minutes that is bringing you down.

Lets say you always make 15 minute trips and that you get 30 MPG for the first 5 minutes and 55 MPG for the last 10 minutes. If you do the math, you will find that (5x30 + 10x55) / 15 = 46 MPG. However, if your trips are always 20 minutes instead, you get (5x30 + 15x55)/20 = 48 MPG. 30 minute trips result in 50 MPG and 10 minute trips result in 42 MPG.

It's as simple as that. You can drive as carefully and smoothly as you want and you will still be limited by the percentage of your trips that is taken up by the warm up cycle.

 

In our first 6 months (2005 model), we never got better than 35 mpg (yikes!), and now, it's tough to even pass 44 - so you're already ahead of me. After reading other posts, I realize it's mostly because my trips are very short, and we have stop signs or pedestrians crossing or unavoidable stop lights at least 4 times per mile. I've been trying to do more of the glide thing, but it doesn't seem to be enough to make up for the things I mentioned. On the other hand, others around here (Berkeley) do get in the 50's - maybe their trips are longer?

 

This must be new as my 2005 resets both the MFD mileage and average mpg readout each time I fill up.

 

We are the same way. My wife uses the car during the week, and the vast majority of her trips are shorties with the car barely going beyond that first 5 minute bar. Are mileage here in NJ (2007 std. Prius) is ~34MPG winter and ~43MPG summer. When we take out the car for longer trips and P&G, the mileage can often be 50+.

On the other hand, we still keep our 2002 Ford Explorer for those hauling needs (e.g. taking my telescopes and gear out to a dark sky location, Prius cannot hold that stuff) and I used it this past week doing the short trip driving and it now has 9MPG for the ~60 miles - so we are kicking butt with the Prius!