Dropping MPG

EllenH · 10-01-2007, 06:31 PM

Last year, toward fall, I noticed a decline in mgp despite no changes in where I drove or driving habits. As it was getting towards fall, I dismissed it as a change in gas formulations. At best over the winter, my 2005 couldn't do better than 40mpg. As the car wasn't used much during the cold months, I pretty much ignored this. With spring I was hoping for better mpg. It did creep up to 48 at times but that was about it. The previous year and a half, my mpg averaged 52-56 for summer and 48-52 colder weather. Now with cold weather approaching (has the formulation been changed yet?) it has dropped down to 42mpg. I asked the toyota mechanic about this and he said as Prius age, there mileage suffers. This doesn't sound right.

Is he correct and should I be looking at a Corolla or other steady mpg vehicle? I am a careful driver, never go over 50 on long trips, keep local trips to a minimum, and don't use air or heat excessively. No problem with the tire inflation either. If I switch mechanics, what should I have them look at. as possible problem areas? The car has 28,000 miles on it.

ACORNBLUES · 10-01-2007, 08:18 PM

Few questions:
1) are you changing your oil and rotating your tires regularly?
2) what pressure do you have your tires inflated to?
Few factoids:
a) in cooler weathers, the ICE (gas engine) stays on more to keep the emissions stuff hot so it can function properly - ppl stuff their front grills w/ pipe insulators to help keep the engine warm
b ) in cooler weathers, the ICE takes longer to warm up - installing an EBH (engine block heater) will help reduce that time.

<div class='quotetop'>QUOTE(EllenH @ Oct 1 2007, 05:31 PM) [snapback]520026[/snapback]</div>

Quote:

Last year, toward fall, I noticed a decline in mgp despite no changes in where I drove or driving habits. As it was getting towards fall, I dismissed it as a change in gas formulations. At best over the winter, my 2005 couldn't do better than 40mpg. As the car wasn't used much during the cold months, I pretty much ignored this. With spring I was hoping for better mpg. It did creep up to 48 at times but that was about it. The previous year and a half, my mpg averaged 52-56 for summer and 48-52 colder weather. Now with cold weather approaching (has the formulation been changed yet?) it has dropped down to 42mpg. I asked the toyota mechanic about this and he said as Prius age, there mileage suffers. This doesn't sound right.

Is he correct and should I be looking at a Corolla or other steady mpg vehicle? I am a careful driver, never go over 50 on long trips, keep local trips to a minimum, and don't use air or heat excessively. No problem with the tire inflation either. If I switch mechanics, what should I have them look at. as possible problem areas? The car has 28,000 miles on it.
[/b]

EllenH · 10-01-2007, 09:00 PM

Having read lots of questions in the forums, I have followed all recommendations. Even switched to synthetic oil. The first year of ownership was perfect even as the temps dropped. Now I find, the older the Prius gets the more the mpg seems to be dropping. What else can I ask them to check out? Nothing has changed (driving locations, method, ) but the Prius now doesn't seem to know its supposed to be the best economical car to own.

paprius4030 · 10-01-2007, 10:15 PM

Our 05 Prius has 75k and mileage hasn't changed at all. My question is...have you changed the engine air filter?

**efusco** · 10-01-2007, 10:30 PM

<div class='quotetop'>QUOTE(EllenH @ Oct 1 2007, 08:00 PM) [snapback]520081[/snapback]</div>

Quote:

Having read lots of questions in the forums, I have followed all recommendations. Even switched to synthetic oil. The first year of ownership was perfect even as the temps dropped. Now I find, the older the Prius gets the more the mpg seems to be dropping. What else can I ask them to check out? Nothing has changed (driving locations, method, ) but the Prius now doesn't seem to know its supposed to be the best economical car to own. [/b]

I've just gone over 65k miles and my last year's mpg is the highest since getting the car. I got 54 in year 2 & 3 and 60mpg this year.
See my thread just posted today: http://priuschat.com/4-Year-Fuel-Eco...ts-t39342.html

EllenH · 10-02-2007, 09:25 AM

Knowing the Prius should be capable of better mpg is even more unsettling. The dealership techs obviously need a little guidance given the answer I received from them previously. Yes all filters have been changed regularly. Any clues as to what needs to be looked at would be appreciated.

bwilson4web · 10-02-2007, 09:35 AM

<div class='quotetop'>QUOTE(EllenH @ Oct 2 2007, 08:25 AM) [snapback]520239[/snapback]</div>

Quote:

Knowing the Prius should be capable of better mpg is even more unsettling. The dealership techs obviously need a little guidance given the answer I received from them previously. Yes all filters have been changed regularly. Any clues as to what needs to be looked at would be appreciated.
[/b]

tires and alignment
transaxle oil change

mikepaul · 10-02-2007, 10:00 AM

I hit a personal all-time record of 59.1MPG over 59 miles in August, so age (and even a weakened wheel bearing) doesn't really impact a Prius that's been decently maintained.

Darn hills around here make these records only possible on road trips, though...

fan-atic · 10-02-2007, 10:04 AM

[As the car wasn't used much during the cold months, I pretty much ignored this. With spring I was hoping for better mpg.]

Could it be the Traction battery? The Prius needs to be driven regularly to keep the NiMH battery from discharging and aging prematurely. I believe the manual says to start it at least every two weeks.

firepa63 · 10-02-2007, 10:24 AM

Did the mileage drop after an oil change? If so, check the level. If it's overfilled you will definitely get an MPG hit.

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10-01-2007, 06:31 PM	#1
EllenH Join Date: Oct 2007 Posts: 4 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Last year, toward fall, I noticed a decline in mgp despite no changes in where I drove or driving habits. As it was getting towards fall, I dismissed it as a change in gas formulations. At best over the winter, my 2005 couldn't do better than 40mpg. As the car wasn't used much during the cold months, I pretty much ignored this. With spring I was hoping for better mpg. It did creep up to 48 at times but that was about it. The previous year and a half, my mpg averaged 52-56 for summer and 48-52 colder weather. Now with cold weather approaching (has the formulation been changed yet?) it has dropped down to 42mpg. I asked the toyota mechanic about this and he said as Prius age, there mileage suffers. This doesn't sound right. Is he correct and should I be looking at a Corolla or other steady mpg vehicle? I am a careful driver, never go over 50 on long trips, keep local trips to a minimum, and don't use air or heat excessively. No problem with the tire inflation either. If I switch mechanics, what should I have them look at. as possible problem areas? The car has 28,000 miles on it.

10-01-2007, 09:00 PM	#3
EllenH Join Date: Oct 2007 Posts: 4 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Having read lots of questions in the forums, I have followed all recommendations. Even switched to synthetic oil. The first year of ownership was perfect even as the temps dropped. Now I find, the older the Prius gets the more the mpg seems to be dropping. What else can I ask them to check out? Nothing has changed (driving locations, method, ) but the Prius now doesn't seem to know its supposed to be the best economical car to own.

10-01-2007, 10:15 PM	#4
paprius4030 Senior Member Join Date: Aug 2004 Location: Pocono's, Pa. Posts: 1,079 My Car: 2008 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 1	Our 05 Prius has 75k and mileage hasn't changed at all. My question is...have you changed the engine air filter?

10-02-2007, 09:25 AM	#6
EllenH Join Date: Oct 2007 Posts: 4 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Knowing the Prius should be capable of better mpg is even more unsettling. The dealership techs obviously need a little guidance given the answer I received from them previously. Yes all filters have been changed regularly. Any clues as to what needs to be looked at would be appreciated.

10-02-2007, 10:00 AM	#8
mikepaul Senior Member Join Date: Dec 2003 Location: Columbia, SC Posts: 1,683 My Car: 2004 Prius Package: #9 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	I hit a personal all-time record of 59.1MPG over 59 miles in August, so age (and even a weakened wheel bearing) doesn't really impact a Prius that's been decently maintained. Darn hills around here make these records only possible on road trips, though...

10-02-2007, 10:04 AM	#9
fan-atic Member Join Date: Apr 2007 Location: Holliston, MA Posts: 59 My Car: 2007 Prius Package: #2 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	[As the car wasn't used much during the cold months, I pretty much ignored this. With spring I was hoping for better mpg.] Could it be the Traction battery? The Prius needs to be driven regularly to keep the NiMH battery from discharging and aging prematurely. I believe the manual says to start it at least every two weeks.

10-02-2007, 10:24 AM	#10
firepa63 Senior Citizen Join Date: Jul 2005 Location: SE Pennsylvania Posts: 436 My Car: 2009 Prius Package: #5 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Did the mileage drop after an oil change? If so, check the level. If it's overfilled you will definitely get an MPG hit.