Low MPG ???

I think the best thing to do is test the car at constant speed on level highway, after fully warm. You can compare instant readings on mpg averaging them in your head, or drive 10 miles and use the reset to give you a more exact mpg number for that constant speed trip. Do the test with cruise control for really constant speed.

It helps to have a nav with altitude readouts so you can prove the road is really level. Sometimes you can't tell by eye accurately.

Then compare to another car, or against the data many have listed here, or find Wayne's Palm simulator, to see what you should be getting.

If you get good mpg readings for this, then you need to examine your driving or your driving conditions for the answer. Usual things that cause people to report lousy mpg are: city driving with too many stops and starts, really big hills, driving like 80 mph, or a very shaky foot on the accelerator, hard (non-regen) braking, short trips, short trips/slow driving in very cold weather, or slow driving in hot weather with AC.

If you are in a windy area you need to account for wind speed and direction and allow for that to affect your mpg. A 10 mph headwind is very noticable, much like driving at 60 mph instead of 50, etc. And a cross wind is bad too.

If something is wrong that causes the engine to switch off less, it might explain someone getting 50 instead of 65 mpg, but would not ever cause mpg to go to under 40 mpg. In winter my engine stays on full time and I can normally stay over 40 mpg, except when doing short trips at like 0 degrees.

 

I'd have to wonder just HOW you are driving?

I got lousy mileage for the first few days then realized after talking with Ray Moore that my technique was the biggest factor. I jumped from lousy high thirties up into the low fifties.

Tire pressure is another issue, have you raised it to 42/40 (front/rear)? That can help too.

As to the AC - I've done all of my driving so far, since June, in the summer heat of Texas. Yes it's October but we'll hit 90 today. AC runs most of the time on my car and has for the whole time I've had it. A few degrees can make a huge difference. Tricks on this score... DON'T let the AC cool down hot air trapped in the car. Open the rear hatch and allow that hot air to rise away. Start the car and switch on the AC. What temp would you ordinarily set the AC to? Try warmer. I feel comfortable at 76 but can have just about as good a comfort zone if I roll up to 78 and toggle on the floor vents allowing my feet and lower legs to be directly cooled. This little change alone made a 2-3 mpg difference.

Teach yourself in an afternoon how to pulse & glide if you are not already doing that in non-highway driving. Speed fairly quicly up to 40mph or so then take your foot off the accellerator pedal. Green arrows turn up right away showing rotational friction feeding back into the battery via regen, right? Well, that's bad, you are slowing down... step VERY delicately on the pedal until you cancel that out. You don't want arrows from either the ICE or electric motor, you want NO ARROWS. It's like balancing a broomstick on your finger tip... just keep trying to get back to the no-arrows GLIDE.

I recommend you do this in either a large parking lot or a back country road with little traffic until you get the hang of it... Soon you will be feeling the sweet spot with an occasional glance at the MDF screen.

Each of these little adjustments adds up, You can drag that MPG average up pretty impressively with only a few small adjustments unless there is somethingwrong with your Prius. I'd bet though on a little TLC helping out tremendously. I've got a student in my class who has a new 3 week old Pri with similar problems, I've given him similar advice and he's now reporting better mileage... and continues to improve

Good luck

Terry

 

As the other posts mention, it's likely your driving habits or the way your driving.

You really just need to get the acquired feel for the car. I always drive with the energy screen up and I watched it a lot at first to get a feel for just how much I could press the pedal before the ICE would kick in. Now, I still get the same mileage regardless of whether I'm focusing on it or not.

The other key is to anticipate what's coming. I may be 1/4 of a mile away from a stop ahead, but it does me no good if I accelerate to get to it. If I just either maintain speed (on EV) or just let the car use it's momentum to keep going, then I'll likely hit the green and not have to accelerate from a stop, which is the biggest hit to fuel economy.

 

It will be near 90F again today in Texas. MPG went up 10% with a drop in temp from above 95F to below 90F. I use AC all the time.

There may be something to the tire pressure suggestion since it is obvious that a full balloon will roll easier than when 80% full. How many MPG that accounts for is hard to tell.

All everyone else has said driving style is the big deal with a Prius. It will zip around quickly if you want it to. The really big deal with the hybrid system is learning to coast to let the regen system charge the battery. If you drive it like a regular car constantly feeding it gas you will get low MPG. If you pulse and glide, coast to stops, coast even when accelerating after you learn how, MPG will more likely improve.

It takes a while to change driving style to get high MPG but it is well worth it financially and in Prius pride.

Goodl Luck!

 

AC will knock it down. Also, a short commute will get you low 40s at best.

Sounds like you're driving it like a "regular" car...

 

john2223,

How far/long do you typically drive it for each trip you make? What temperature do you set the A/C at?

Short trips will definately cut down on your milage, since the Prius gets gas milage in the 30's for the first 5 minutes or so until the engine heats up. Heavy A/C use will also affect your milage. The hybrid battery drains quickly when the A/C is running hard, so the car spends a lot of time charging the battery back up.

From what I've read, most people here set the temp in the mid to upper 70's when it's around 90 degress or above. If you are setting your temp to something like 68 degrees, then your A/C is working very hard to get the temperature down. If that is coupled with short trips, it just makes things worse.

 

The others covered it all.

I noticed you said driving with AC off didn't improve it. How long a trial were you able to give this? Less than, say, 100 continuous miles won't tell you much.

Many of us, depending on climate, get our worst MPG in BOTH summer and winter, and our best in spring and fall.

That said, I'm one of those who believes "not all Priuses are manufactured equal". This is a little-discussed issue. After all, what's to say? :blink: I've already owned three Priuses, and I KNOW they don't all equally "move into stealth mode", even with that small a sample.

Yes, it takes a "sensitive foot", but I still don't think they all perform exactly the same.

Hmmm---sounds like grist for another poll...

 

In regards to highway driving, I think you'll find (on fairly level terrain) that you can maintain 60-70mph and still get 50-70mpg (again, 70mpg as your are level - it will drop as you go up small inclines - hills are probably more likely in the 20's)

 

I think your AC use and short trips are the cause of about, um, 95% of your MPG problem.

Good grief, you do like to stay cool, dontcha? I set mine on 75.

Good luck. If your domestic duties have you locked into those short trips, though, you'll be lucky to get MPG into the low 40's.

 

I just got my Prius Sept 1st, and there were many hot days. I like it cool, so I had my AC set around 70 - sometimes 68 or 69. I still have averaged (since I got it) 50mpg.

So personally, I haven't found it affects it all that much.