2006 prius only getting 35mpg

Hi Mullen28, here are a few question that might be relevent.

- What exactly is the temperature like in Philly at the moment and do you make a lot of short trips? How long does it take for the engine (ICE) to warm up after starting your morning drive (when warm it will cut out when stopped or gliding).

- What are the brand/model of tires and what is the inflation pressure.

- Does your car seem to "glide" ok? This is when you back off the accelerator and the ICE cuts out, especially when coasting to stop or going downhill.

- Have you checked the MFD readout with actual gas station measurements of MPG. Most people report the MFD readout fairly accurate but my prius is one of the apparent few that reads lower than the actual gas station measured value (I actually do about 12% better than the MFD readout). If you make your own mpg measurements then make sure you average them over several tank fulls since you have the gas tank rubber bladder in North America.

 

How long is your commute in miles and minutes? I see fuel economy gains for the first 15 minutes, so if you commute is less than this it may not be warm by the time you get where you are going.

 

Search in the Gen II fuel economy forum for a very recent entry - maybe a week ago or less - concerning a guy who was having low mpg issues until he replaced the 12 V battery. He went from mpg's in the thirties to nearly 50 with the new battery.

Three years seems a little soon, but you can check the battery voltage or have the battery tested.

 

Test your battery first as there is quite possibly nothing wrong with it.

Higher tire pressures give lower rolling resistance - at the expense of a slightly rougher ride. So inflate to a at least the recommended.

Luckily we don't have the bladder in Australian models so I've never had the problem, but I hear it makes it difficult to get a consistent fill volume. So you probably wont get a very accurate picture until you averaged it over three or four tank fulls anyway.

 

You can't. Just fill it up till the first click of the pump handle and call it good. I arely get more than 7.5ga in my tank after driving it to the second pip (mark on the gas gauge). It's just something you have to deal with.

 

Mullen28, welcome "neighbor". Short stop & go trips will kill the fuel economy. On average I see 25mpg for the 1st 5 minutes & 50mpg for the 2nd 5 minutes.

First, inflate your tires. Harder tires last longer & will improve FE. Even at the nominal 45psi I've been told I have edge wear indicative of underinflation.

Second, block the grill to keep what little heat the ICE is generating. Tony S started the ultimate grill blocking thread.

Third, accelerate briskly. Instantaneous MPG = half MPH.

Fourth, keep an eye on the 12V battery voltage.
You can easily check out your battery status/charging system using the MFD in maintenance mode. No tools required.

1. Get your Prius into "Accessory Mode" - Press the power button without touching the brake pedal.
2. Put the MFD into "Maintenance Mode" - Press and hold the "Info" button on the MFD while turning the headlights on and off 4 times.
3. Press the "Menu" field on the screen.
4. Press the "Display Check" field.
5. Press the "Signal Check" field.
6. The 12v battery voltage will be one of the items listed, it should be above 12 volts. If it is lower, either the battery needs replacement or the charging system is not functioning correctly - see step 7.
7. Put a small load on the battery by pressing the power button again without touching the brake pedal. The voltage should stay above 12v. If it drops significantly, you need a new battery.
8. Now get your Prius into "Ready Mode" - step on the brake and press the power button. The battery voltage should immediately rise to 13.8 volts (Your Prius uses constant voltage charging). If it is lower, the battery will never charge; if it is much above 14 volts, your 12v battery will get cooked.
9. Shutting the car down will reset the system back to normal operation.

If you need to get a new 12v battery, you can opt for a dealer replacement or get a better battery at a lower price at: http://www.elearnaid.com/12vo1topraub.html
and install it yourself.

JeffD

 

I've had a recent drop in MPG and tried this. (Really useful thing to know!)
My voltage was 12.2 (it was lower the first time and got worried until I realised that the lights were still on... dur!)
On step 7 it droppped to 11.9- is that a "significant" drop? Probably not but I thought I'd ask.
On step 8 it rose to 14.4- is that too high or within reasonable limits? Don't want a cooked battery!
I've only just had a service and nothing seemed to come up on that.
I've had a drop from 58ish to 47 at best. Maybe it's just the wet and windy weather recently over here. It's my first winter with the Prius so please feel free to tell me I'm worrying over nothing!

 

That's a little low mullen. The exact figures will vary a bit depending on the temperature and how long it's been standing since last driven, but I'd want to see values above 12 for the first two readings. For example my battery is getting a bit old (over 4 years) and it still manages 12.4 for the first reading and 12.1 for the second.

 

12 Volt My Guess, been there done that

 

I live in California and out here we have a winter blend gasoline that on average drops my mileage by 10-15 %. It starts showing up in gas pumps abount the end of September or early October. I do not know about the East coast winter blend fuel. Here, the mixture includes an oxogenate to reduce smog in colder weather. It will cause the average MPG to drop from ~48 in summer to 39-40 in winter. I run my tires at 42 in front, 40 rear and check them bi monthly with a digital psi gauge.. If they get below about 38 PSI my milaege will drop by another 5-10 % Short trips on cold mornings kill MPG. Good luck and read findings here at Prius chat as written by others on fuel economy. You will learn a lot.
-Paul R. Haller-

 

Mullen28 - I'm also in the Philly area and have a similar driving pattern - a 7 mile commute during the week (suburbs so only a few stops) and then a mixed bag on weekends. Since the weather has gotten cold in the past few weeks I have been getting in the high 30's during the week. In the summer with the same routine mileage is in the mid-40's.