My Prius only getting 35mpg

<div class='quotetop'>QUOTE(DreamcastDC @ Jul 1 2007, 01:30 AM) [snapback]470909[/snapback]</div>

Two reasons I can think of:
1) Very short 5-min trips, perhaps with blasting the AC on
2) You are coming to this figure using gas *pumped* rather than the MFD reading. Because of the variation of the bladder in the US Prius tank you need to average about 4 tanks of gas pumped to get a more accurate figure.

Other contributors to low gas mileage:
1) Tires are under inflated. Pump 44/42 psi in them. Also your tires are really new.
2) Poor regenerating technique. Coast as much as possible. Break progressively to a stop to increase the battery's charge.
3) Accelerating too fast. A useful suggestion someone game me is that your MPH must never be higher than double than your mpg. You are accelerating too fast that way.
4) Accelerating too slowly. Learn to glide using a yellow arrow condition only eg. when going slightly downhill
5) Horrendous red traffic light timing!

 

<div class='quotetop'>QUOTE(DreamcastDC @ Jul 1 2007, 01:30 AM) [snapback]470909[/snapback]</div>

Greetings: to start with, make sure the tires are at 42psi front/40 psi back...additionally, your mileage will increase as you approach 5000,10000, etc...miles as the engine loosens up...other helpful concepts on mileage, are...dont accelerate like a bat out of h@#$...also coast to red lights as traffic permits...bear in mind driver break in is needed to learn to drive "correctly"...most drivers are clueless on how to save gas, as seen on your local freeways...pulse and glide techniques as noted on the forum are excellent ways to increase mileage...a sweet spot is 35-41mph to stay on battery...Use the A/C minimally and set it at 78 degrees as it will make a difference on mpg...just a few tips which ive used over the last 3 years....

 

I haven't done the tire mod and I still average 53.

I'd be willing to bet the OP drives fast and accelerates hard and doesn't glide. Those are where the biggest gains are made, particularly P&G.

 

I only am averaging 35 mpg right now and I know it's because of my very short hop to work and back, plus I go home for lunch every day. I also don't put a lot of miles on weekends, but when I do I get decent mileage. When we meet I want someone - maybe hobbit - to drive my car and tell me if you think the alignment is off. Seems to pull to the left when braking sometimes - even sometimes on the highway. I also carry supplies for my volunteer group around in my car which makes it heavier than it could be. During the last two weeks in Feb. when I first got the car, I was getting 40-47 doing highway driving back and forth on a daily trip to the south shore (about 80 miles round trip) to visit a hospitalized family member, and that was before I ever heard about pulse & glide or pumping up the tires. That being said, I would be getting far worse mileage if I was still driving my Corolla. So there are many factors that influence how much mpg one gets. I still consider myself in the learning stage with room for improvement.

 

<div class='quotetop'>QUOTE(DreamcastDC @ Jul 1 2007, 02:48 AM) [snapback]470945[/snapback]</div>

I also developed a pull to the right when braking and thought I had an alignment problem. When I took my 06 Prius in for a routine service, the manager came out and told me I didn't need an alignment. Instead, the mechanic found varying tire pressures, e.g., left front was 36 and right front was 41. The rear tires were also different, but the steering is up front and would be more noticeable. The tires were adjusted to 36/33 and the car drives beautifully. I tried inflating to the suggest 42/40 from some users, but the ride was unacceptable for a one or two gained in MPG.

 

<div class='quotetop'>QUOTE(Neicy @ Jul 1 2007, 07:38 AM) [snapback]470965[/snapback]</div>

Cold weather means lower gas mileage. I was averaging 44 mpg or a tad less during the coldest part of the winter. Now that we have summer weather, I easily average 50 mpg.

As others have said, you must train your brain to coast. I still have to remind myself to get off the gas pedal just as soon as I can, which often times is way sooner than what I was used to. You really can coast to that next red light, and from a long distance. You have to do this to get the full potential from the Prius.

I do have some extra air in my tires, although I haven't seen that much difference from adding air. You must be sure that tire pressures are at least as high as what is called for. A little extra means you won't dip below those values over time.

Harry


<div class='quotetop'>QUOTE(TonyPSchaefer @ Jul 1 2007, 10:45 AM) [snapback]470993[/snapback]</div>

Corrected link: http://www.chicagopriusgroup.com/resources...EPA-Mileage.pdf

Harry

 

It is simple to determine whether dragging rear brakes are contributing to low fuel economy. Starting from cold, drive a mile or two on generally level ground. Then stop and feel each of the rear brake drums. Wet your finger first just in case the drums are hot. If they are cool the possibility is eliminated. If they are hot, then either your parking brake cable is too tight or the 'self-adjusters' need to be checked.

 

<div class='quotetop'>QUOTE(zqfmbg @ Jun 30 2007, 10:55 PM) [snapback]470929[/snapback]</div>

What tire mod are you talking about? If you are talking about increasing the tire pressure, that is not a mod.

 

<div class='quotetop'>QUOTE(DreamcastDC @ Jul 1 2007, 12:30 AM) [snapback]470909[/snapback]</div>

That could correspond to:

1) Average speeds around 85 mph
2) Lack of a block heater in colder climates
3) Many short trips of 5-10 minute duration w/o a block heater
4) Overfilled oil pan
5) Tire pressures less than maximum sidewall
6) Undiagnosed alignment problem
7) Aggressive use of accelerator



Bob Wilson

 

Could you tell us your driving routine? 35 is low. My 1992 Corolla gets 36 mpg, so your Prius should do much better.

 

<div class='quotetop'>QUOTE(DreamcastDC @ Jul 1 2007, 12:30 AM) [snapback]470909[/snapback]</div>

I notice you are in the San Francisco area. Do a lot of hills? How about commute-time stop and start driving? A lot of the posters are fortunate to be in flatland areas which makes it easier to max out the mileage. Learn the accelerator feathering and gliding and other techniques the board has suggested. You will "get it" soon enough.

 

Start here: http://priuschat.com/index.php?autocom=art...rticle&id=3 and http://priuschat.com/New-owner-Want-MPG-he...rst-t15311.html.

To the OP, what kind of mileage were you expecting and why?

 

I just got my Prius on Tuesday. I have 166 miles on it and my screen shows my Consumption Screen shows me to be at 49.8 MPG. Since we are both Prius beginners its easy to relate to the big big driving change. I was really worried this morning on my way to work because it is mostly highway and I was thinking I was going to get horrible milage. But when I reached my parking lot at work it showed 52.2 MPG. I was between 60-70 mph the whole time. A few things I do when driving....


Drafting: Find someone who is driving the same speed as you and follow behind them. Cutting down on your wind resistance really effects on how hard your car has to work. ((FYI: Your car has to work 8 times harder to go 65 mph over 55))


Hills: Try not to accelerate up hills, try to maintain your speed all the way to the top and try to coast/accelerate on the backside of the hill.


Battery Useage: At high speeds; When you reach the speed you want to maintain quickly release your foot from the gas pedal then lightly press it. To me it feels like Its just accessing the battery. If/when you start to drop down a few MPH slowly press it until you stop. If you can take a look at the consumption screen while you do this you can see your MPG jump around 50-80. Its that state that it seems to get the best MPG. I dont know whats exactly happening as the arrows jump all around constantly. But my theory is that you are making the battery work its best (80's mpg) and when it runs down to 80% the I.C.E. charges it back up (50's mpg) and then it goes back to using battery power again (80's mpg). Its really really wierd. If you can go a maintained speed try to get that to happen.

At low speeds; Get up to speed 30-40 mph and release the gas then lightly press on it again and try and get only the battery to run. Its there that you will see a steady 99.9 mpg on the consumption screen.




After you get used to getting the battery to doing work you will start to see how important good coasting and braking is as that is the easiest way to get your battery up to a full charge. I wish I had a good slow/coasting spot in the middle of my way to work so I could make sure my battery gets a good (easy) charge. Oh yeah, Dont rush to stop signs and stop lights... if you dont have to.

 

<div class='quotetop'>QUOTE(Vadercar @ Jul 5 2007, 12:53 PM) [snapback]473549[/snapback]</div>

Most of these points are valid, some are close but your understanding of the car isn't quite right, but obviously you're learning how your driving affects the energy system and MPG. Soon you will grok the engine/motor/battery interplay.

True. Obviously you need to be careful while doing this. The drafting effect drops with distance but is still noticeable at over 1 second behind an 18-wheeler, according to Mythbusters, so you don't have to be tailgating. (Most states have a 2-second rule for safe driving, but it's never followed in urban environments).

True. This could be part of the OP's problem - San Francisco doesn't have much in the way of cold weather or A/C usage, so I don't think that's driving down his mileage (so to speak), but the quick accelerations, especially up hill could be. I can get better mpg on low rolling hills than flatland, but don't have much experience on big hills.

The technique is pretty close. When you're in the 50-80mpg at highway speeds, tiny variations will make the engine work harder or not, and that's needed to keep you at a constant speed. You should recheck the information posted on pulse-and-glide. Basically you get up to speed as quickly as you can without pulling energy from the battery, and glide or coast (they're different, in case you didn't know) down to a few mph below that speed (or 10 mph lower, depending on traffic conditions, don't get anybody too upset), then accelerate again. If you can time your accelerations to uphills (when you have to accelerate anyway) and coast or glide on downhills, you can really get good mileage on low hills.

Actually you might be talking about glide, where there are no arrows in the energy screen. The battery is not involved and the engine isn't turning (above 40 mph it will turn because of transmission reasons, but no fuel goes thru it when showing 99.9 mpg and the valves are open to reduce internal resistance). So what you really want is no battery.

Again, you don't want to use the battery. The purpose of the battery is to allow Toyota to make a family car with modern performance expectations while using a small engine. So the battery helps out when you need to accelerate. Sometimes it makes sense to use the battery alone (for a short time if the engine is already off, and there's plenty of charge in the battery). But keep in mind, all power in the battery came from the engine, either directly or by recovering kinetic energy thru the brakes, it's just stored for when it's needed. This isn't as efficient as using the energy directly. The hypermilers (people who get over 65mpg in a Prius) rarely use the battery at all, and their consumption screens don't have many (or any!) regen cars in the display.

 

These are all good ideas. For myself, I just drive the car like I would any other. I use the AC whenever, and however cold or hot that is comfortable, and I accerarate with or even ahead of most traffic. I do 99% freeway, 90 miles a day, CC whenever I can. I pumped up the tires to about 40/38 for improved road handling. I am getting 50.1 average (by the MFD), and tanks vary between 47 and 53 (calculated), without even trying. Your mileage may vary...

I think the duration and terrain on which you drive will have the most effect. Pump the tires up, don't obsess. 35 is far better than any car I've ever driven. 50 is better though

 

We have 4 Prius's in the family. Mine is an '04 with 50K miles, my wife has an 06 with 10K. She has consistantly been getting only 44-45 MPG and I've consistantly been getting 49-50. I thought it was related to her driving style, but we've traded cars and it's not that. So, temperature, gas brand, tire pressure, terrain, etc all the same or close. Her MFD rarely changes from 44.6 and tank fill calculations similar, long trips or short.

Been to the dealer and eventually had the district tech involved. Keep telling us that nothing can be done. Just picked up on the dragging rear brake test suggestion and drove a short distance, found slight heating, I'll have to go a couple of miles and see. Sure sound like something dragging with that constant MFD.

Are we the only ones with this problem??

Arnie

 

<div class='quotetop'>QUOTE(arniesalsared @ Jul 6 2007, 03:36 PM) [snapback]474219[/snapback]</div>

Can you post the last wheel alignment numbers for both vehicles?

Thanks,
Bob Wilson