Mpg decreasing

momstoys · 10-25-2005, 06:32 PM

When we bought our Prius, the temps were about what they are now; 40-50 daytime. From the start, we were getting 52-54mpg for local driving (city-short trips) and 58 on the highway for long trips. For the last two tanks of gas, the mileage has dropped to 35-38 for local driving and only gets up to 50 on long trips. Driving style hasn't changed and I checked the air pressure. Any clues? My husband thinks the car is running a bit rough but I don't hear it. There are about 7700 miles on the car now. We are 180 miles from the dealership (one that I trust) so hoping it is something simple.

skruse · 10-25-2005, 06:53 PM

Quote:

Originally posted by momstoys@Oct 25 2005, 02:32 PM
When we bought our Prius, the temps were about what they are now; 40-50 daytime. From the start, we were getting 52-54mpg for local driving (city-short trips) and 58 on the highway for long trips. For the last two tanks of gas, the mileage has dropped to 35-38 for local driving and only gets up to 50 on long trips. Driving style hasn't changed and I checked the air pressure. Any clues? My husband thinks the car is running a bit rough but I don't hear it. There are about 7700 miles on the car now. We are 180 miles from the dealership (one that I trust) so hoping it is something simple.

[snapback]145472[/snapback]

We don't know your geographical location, but suspect it is several factors:
1) new Prius owners-drivers
2) onset of cooler autumn-winter weather
3) Prius is not yet "broken in" with more than 10k mi (16k km)

Fuel economy always takes a drop with cooler-colder ambient air temperatures.

hdrygas · 10-25-2005, 08:22 PM

Also winter gas formulations in some areas can cause a drop in MPG. Around here that happens in October both last year and again this year I noticed a drop of 4-5 mpg from one tank to the next at this time of year.

aka007ii · 10-25-2005, 08:31 PM

Quote:

Originally posted by hdrygas@Oct 25 2005, 05:22 PM
Also winter gas formulations in some areas can cause a drop in MPG. Around here that happens in October both last year and again this year I noticed a drop of 4-5 mpg from one tank to the next at this time of year.

[snapback]145503[/snapback]

Wow, 4-5 mpg drop just with different mixture. It's been hard enough getting over 50 and now I may have to try just as hard to get in the high 40s? Oh brother.

catsbox · 10-25-2005, 09:42 PM

I noticed a significant drop in the mpg this last tank. I am certain it is the winter gas as everything else has stayed pretty much equal. I took a good 5 mpg hit.

dreichla · 10-26-2005, 07:03 AM

I too have noticed a significant drop since we've been in these cooler temps. I've also noticed I take a big hit (more than usual) during my first 5 minutes of driving.

I was interested to see some threads about block heaters and radiator coverings to minimize the warm-up time at engine start.

I ordered a block heater. We'll see. . .

**TonyPSchaefer** · 10-26-2005, 07:43 AM

Every time someone mentions dropping mileage in the winter, I point them to my lifetime mileage chart to show that they are not alone. Click the link in my signature.

momstoys · 10-26-2005, 10:34 AM

I would have thought of the temps changing BUT it is now the same temps as when we bought it in early March before they would have switched to summer gas formulations. Any possibilities that the formulations are now drastically different due to the Katrina, etc.? Driving methods just don't change which is why I got the much appreciated mpg before. I am going to have to check the mpg in my other vehicle and see if it has changed too. We are in NW MI

galaxee · 10-26-2005, 10:53 AM

using the heater yet? that will make the ICE run more, and decrease MPG.

tomdeimos · 10-26-2005, 02:29 PM

When I changed my first oil fill it looked much thinner than my 5W-30. I think that made my mpg drop a bit when I lost the break in oil.

Beyond that slight temperature differences have a big effect and not just the current temp when you start out in the morning. Battery temp will depend more on the min temp overnight.
Till it gets warm the engine races more and burns more fuel.

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10-25-2005, 06:32 PM	#1
momstoys Junior Member Join Date: Dec 2004 Posts: 26 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	When we bought our Prius, the temps were about what they are now; 40-50 daytime. From the start, we were getting 52-54mpg for local driving (city-short trips) and 58 on the highway for long trips. For the last two tanks of gas, the mileage has dropped to 35-38 for local driving and only gets up to 50 on long trips. Driving style hasn't changed and I checked the air pressure. Any clues? My husband thinks the car is running a bit rough but I don't hear it. There are about 7700 miles on the car now. We are 180 miles from the dealership (one that I trust) so hoping it is something simple.

10-25-2005, 08:22 PM	#3
hdrygas Senior Member Join Date: May 2004 Location: Olympia Wa Posts: 3,650 My Car: 2004 Prius Package: #9 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Also winter gas formulations in some areas can cause a drop in MPG. Around here that happens in October both last year and again this year I noticed a drop of 4-5 mpg from one tank to the next at this time of year.

10-25-2005, 09:42 PM	#5
catsbox Senior Member Join Date: Apr 2005 Location: Bellevue, WA Posts: 251 My Car: 2005 Prius Package: #6 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	I noticed a significant drop in the mpg this last tank. I am certain it is the winter gas as everything else has stayed pretty much equal. I took a good 5 mpg hit.

10-26-2005, 07:03 AM	#6
dreichla Join Date: Feb 2005 Location: Connecticut Posts: 2,230 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	I too have noticed a significant drop since we've been in these cooler temps. I've also noticed I take a big hit (more than usual) during my first 5 minutes of driving. I was interested to see some threads about block heaters and radiator coverings to minimize the warm-up time at engine start. I ordered a block heater. We'll see. . .

10-26-2005, 07:43 AM	#7
TonyPSchaefer Ruler of Omicron Persei 8 Join Date: May 2004 Location: Far-North Chicagoland Posts: 8,415 My Car: 2004 Prius Package: #9 Nominated 4 Times in 2 Posts TOTM Awards: 0 Friends: 16	Every time someone mentions dropping mileage in the winter, I point them to my lifetime mileage chart to show that they are not alone. Click the link in my signature.

10-26-2005, 10:34 AM	#8
momstoys Junior Member Join Date: Dec 2004 Posts: 26 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	I would have thought of the temps changing BUT it is now the same temps as when we bought it in early March before they would have switched to summer gas formulations. Any possibilities that the formulations are now drastically different due to the Katrina, etc.? Driving methods just don't change which is why I got the much appreciated mpg before. I am going to have to check the mpg in my other vehicle and see if it has changed too. We are in NW MI

10-26-2005, 10:53 AM	#9
galaxee running WOT until out of fuel Join Date: Mar 2005 Location: central NC/ western WI Posts: 9,075 My Car: 2005 Prius Package: #5 Nominated 5 Times in 3 Posts TOTM Awards: 0 Friends: 21	using the heater yet? that will make the ICE run more, and decrease MPG.

10-26-2005, 02:29 PM	#10
tomdeimos Join Date: Feb 2004 Location: Lexington, MA Posts: 995 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	When I changed my first oil fill it looked much thinner than my 5W-30. I think that made my mpg drop a bit when I lost the break in oil. Beyond that slight temperature differences have a big effect and not just the current temp when you start out in the morning. Battery temp will depend more on the min temp overnight. Till it gets warm the engine races more and burns more fuel.