what the #$$%^ my MPG ....

happy2472 · 08-08-2009, 06:09 AM

Ok i need some serious help here. Maybe i am mind fing the whole MPG thing but i am going crazy. The pictures i included are from 6 am this morning ... i filled up in NJ and drove to long island NY where i work. I think my 2006 Prius is what a 12 gallon tank and if so if im averaging 42.7 miles per gallon and drove 121 miles ... shouldn't i have only used roughly only 3 or 4 gallons????? My gas gauge is showing half a tank .. wouldn't that be 6 gallons used? I have been under the assumption if the car is to average 50 MPG ... wouldn't i be able to drive 600 miles on a full tank? I did have the AC set to 72 degress like someone said in another post .. no aggressive driving ... i am just so dam confused with this. Can anyone help or give me some input? Maybe i need a tune up? I just had my oil changed roughly 1 month ago. Please HELP ME!!!!!!

krousdb · 08-08-2009, 07:49 AM

There is a reason that we call the Gas Gauge the "Guess Gauge". First, because the tank has a bladder (search forum for more info) the capacity of the tank is less than 12 gallons. Normally, after the add fuel warning comes on, I only get 8 gallons before the pump clicks off. When it is cold outside, you have less capacity. Secondly, the gauge is not linear. You cant use it to tell how many miles you can go. Once you get a few tanks under your belt, you will get a better feel for it. When the last bar on the gauge starts flashing, stop for gas.

As for your assumption, no, you won't be able to go 600 miles if you get 50 MPG. More like 400 miles.

Shawn Clark · 08-08-2009, 03:05 PM

The bladder tank's effective capacity from full to flashing pip is ~8-10 gallons for most of us. (9.95 gallons is my max so far, some get more, some less.) The flashing pip is ~1/8th tank, similar to the E line of analog gauges of other Japanese vehicles I've owned. The bladder however makes the reserve capacity variable (just like the fill volume) so the flashing pip means get gas ASAP.

elcorazon · 09-12-2009, 12:00 PM

I usually can only get between 8-9 gallons when I fill up (always when down to the last pip, sometimes after it is flashing). Depending on your trips you may be getting closer to 40 than 50, possibly under 40 when temps drop and if trips are short (I get closer to 30 in the dead of winter with short trips). I rarely can make 400 miles on a tank. Usually between 350-375 is normal for me.

yardman 49 · 09-12-2009, 12:10 PM

Quote:

Originally Posted by happy2472

Ok i need some serious help here. Maybe i am mind fing the whole MPG thing but i am going crazy. The pictures i included are from 6 am this morning ... i filled up in NJ and drove to long island NY where i work. I think my 2006 Prius is what a 12 gallon tank and if so if im averaging 42.7 miles per gallon and drove 121 miles ... shouldn't i have only used roughly only 3 or 4 gallons????? My gas gauge is showing half a tank .. wouldn't that be 6 gallons used? I have been under the assumption if the car is to average 50 MPG ... wouldn't i be able to drive 600 miles on a full tank? I did have the AC set to 72 degress like someone said in another post .. no aggressive driving ... i am just so dam confused with this. Can anyone help or give me some input? Maybe i need a tune up? I just had my oil changed roughly 1 month ago. Please HELP ME!!!!!!

Hello Happy:

I see that you're new here. Spend some time searching the threads on the G2 gas tank issues cause by a combination of the "bladder" used in the tank, as well as the way that the "guess gauge" works.

A well documented issue. Nothing to be alarmed about, although it can be annoying.

JimboPalmer · 09-12-2009, 01:40 PM

I tend to refill my tank by mileage rather than by the gauge, at 400 miles, I am in the mood to stop and stretch anyways. Once the last pip starts blinking you are in desperation mode, I have gone as many as 30 miles, but run dry in as few as 7 miles. I always try to get gas BEFORE it blinks.

At the other end of the tank, I go from 100 miles to 160 miles before the first pip disappears, so it is not accurate when full either. I plan my fill ups at 400 miles, I find it less stressful. (I have not been in a winter yet, and may need to re-assess my distance once I know my winter mileage. Of perhaps not, winters seem mild here 42 MPG average so far)

EZW1 · 09-12-2009, 01:44 PM

You may need to recalibrate the AZ/EL sensors. They affet the gauge readout accuracy

Shawn Clark · 09-13-2009, 09:53 PM

There is nothing really unusual about the top of the tank being above the top pip indicator--certainly no reason to suspect the sensor calibration. That's normal in every other vehicle I've had. It represents the portion above the Full mark and is usually about 1/8th tank in my experience.

The difference with the bladder is that the top and bottom levels are highly variable. It's nothing unusual to have have the fill vary by 10% or more in back to back fills with similar conditions. Previous tank I did at 52 mpg took 10 gallons (new record fill), this one took just shy of 9 gallons at 50 mpg...despite being 18 miles more.

When you have a problem is when your tank goes empty before the flashing pip. The flashing pip should be about 1/8th tank indicated (to dead empty). That is the norm in other vehicles. Obviously something isn't right if the tank goes empty before the flashing pip.

Muhahahahaz · 09-14-2009, 10:46 PM

Quote:

Originally Posted by krousdb

There is a reason that we call the Gas Gauge the "Guess Gauge". First, because the tank has a bladder (search forum for more info) the capacity of the tank is less than 12 gallons. Normally, after the add fuel warning comes on, I only get 8 gallons before the pump clicks off. When it is cold outside, you have less capacity. Secondly, the gauge is not linear. You cant use it to tell how many miles you can go. Once you get a few tanks under your belt, you will get a better feel for it. When the last bar on the gauge starts flashing, stop for gas.

As for your assumption, no, you won't be able to go 600 miles if you get 50 MPG. More like 400 miles.

Umm... I only get 45 MPG and I've gone 480 miles easy.

Sandy · 09-14-2009, 11:09 PM

I get 200 miles on my first gas blip

08-08-2009, 06:09 AM	#1
happy2472 Junior Member Join Date: Jun 2009 Location: NY Posts: 7 My Car: 2006 Prius Model: N/A Package: N/A Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	what the #$$%^ my MPG .... Ok i need some serious help here. Maybe i am mind fing the whole MPG thing but i am going crazy. The pictures i included are from 6 am this morning ... i filled up in NJ and drove to long island NY where i work. I think my 2006 Prius is what a 12 gallon tank and if so if im averaging 42.7 miles per gallon and drove 121 miles ... shouldn't i have only used roughly only 3 or 4 gallons????? My gas gauge is showing half a tank .. wouldn't that be 6 gallons used? I have been under the assumption if the car is to average 50 MPG ... wouldn't i be able to drive 600 miles on a full tank? I did have the AC set to 72 degress like someone said in another post .. no aggressive driving ... i am just so dam confused with this. Can anyone help or give me some input? Maybe i need a tune up? I just had my oil changed roughly 1 month ago. Please HELP ME!!!!!! Attached Thumbnails

08-08-2009, 07:49 AM	#2
krousdb Senior Member Join Date: Jul 2005 Location: Raleigh, NC Posts: 405 My Car: 2004 Prius Model: I Package: #7 Thanks: 9 Thanked 297 Times in 185 Posts Friends: 10	Re: what the #$$%^ my MPG .... There is a reason that we call the Gas Gauge the "Guess Gauge". First, because the tank has a bladder (search forum for more info) the capacity of the tank is less than 12 gallons. Normally, after the add fuel warning comes on, I only get 8 gallons before the pump clicks off. When it is cold outside, you have less capacity. Secondly, the gauge is not linear. You cant use it to tell how many miles you can go. Once you get a few tanks under your belt, you will get a better feel for it. When the last bar on the gauge starts flashing, stop for gas. As for your assumption, no, you won't be able to go 600 miles if you get 50 MPG. More like 400 miles.

08-08-2009, 03:05 PM	#3
Shawn Clark Senior Member Join Date: Aug 2008 Location: Midwest Posts: 2,071 My Car: 2008 Prius Model: Package: #2 Thanks: 112 Thanked 103 Times in 85 Posts Friends: 0	Re: what the #$$%^ my MPG .... The bladder tank's effective capacity from full to flashing pip is ~8-10 gallons for most of us. (9.95 gallons is my max so far, some get more, some less.) The flashing pip is ~1/8th tank, similar to the E line of analog gauges of other Japanese vehicles I've owned. The bladder however makes the reserve capacity variable (just like the fill volume) so the flashing pip means get gas ASAP.

09-12-2009, 12:00 PM	#4
elcorazon Member Join Date: Sep 2007 Location: chicagoland Posts: 63 My Car: 2007 Prius Model: Package: #3 Thanks: 2 Thanked 0 Times in 0 Posts Friends: 0	Re: what the #$$%^ my MPG .... I usually can only get between 8-9 gallons when I fill up (always when down to the last pip, sometimes after it is flashing). Depending on your trips you may be getting closer to 40 than 50, possibly under 40 when temps drop and if trips are short (I get closer to 30 in the dead of winter with short trips). I rarely can make 400 miles on a tank. Usually between 350-375 is normal for me.

09-12-2009, 01:40 PM	#6
JimboPalmer Tsar of all the Rushers Join Date: Apr 2009 Location: Greenwood MS USA Posts: 378 My Car: 2009 Prius Model: N/A Package: #5 Thanks: 17 Thanked 66 Times in 53 Posts Friends: 3	Re: what the #$$%^ my MPG .... I tend to refill my tank by mileage rather than by the gauge, at 400 miles, I am in the mood to stop and stretch anyways. Once the last pip starts blinking you are in desperation mode, I have gone as many as 30 miles, but run dry in as few as 7 miles. I always try to get gas BEFORE it blinks. At the other end of the tank, I go from 100 miles to 160 miles before the first pip disappears, so it is not accurate when full either. I plan my fill ups at 400 miles, I find it less stressful. (I have not been in a winter yet, and may need to re-assess my distance once I know my winter mileage. Of perhaps not, winters seem mild here 42 MPG average so far) __________________ I tried to remain childlike, but all I achieved was childish. Last edited by JimboPalmer; 09-12-2009 at 01:44 PM.

09-12-2009, 01:44 PM	#7
EZW1 Senior Member Join Date: Aug 2008 Location: Phoenix, AZ Posts: 597 My Car: 2009 Prius Model: N/A Package: #5 Thanks: 0 Thanked 23 Times in 19 Posts Friends: 1	Re: what the #$$%^ my MPG .... You may need to recalibrate the AZ/EL sensors. They affet the gauge readout accuracy

09-13-2009, 09:53 PM	#8
Shawn Clark Senior Member Join Date: Aug 2008 Location: Midwest Posts: 2,071 My Car: 2008 Prius Model: Package: #2 Thanks: 112 Thanked 103 Times in 85 Posts Friends: 0	Re: what the #$$%^ my MPG .... There is nothing really unusual about the top of the tank being above the top pip indicator--certainly no reason to suspect the sensor calibration. That's normal in every other vehicle I've had. It represents the portion above the Full mark and is usually about 1/8th tank in my experience. The difference with the bladder is that the top and bottom levels are highly variable. It's nothing unusual to have have the fill vary by 10% or more in back to back fills with similar conditions. Previous tank I did at 52 mpg took 10 gallons (new record fill), this one took just shy of 9 gallons at 50 mpg...despite being 18 miles more. When you have a problem is when your tank goes empty before the flashing pip. The flashing pip should be about 1/8th tank indicated (to dead empty). That is the norm in other vehicles. Obviously something isn't right if the tank goes empty before the flashing pip.

09-14-2009, 11:09 PM	#10
Sandy Hippi Chick Join Date: Apr 2009 Location: Ocala,Fl Posts: 647 My Car: Other Non-Hybrid Model: N/A Package: #2 Thanks: 53 Thanked 34 Times in 29 Posts Friends: 8	Re: what the #$$%^ my MPG .... I get 200 miles on my first gas blip