City Mileage 10 MPG worse than Higheway Mileage

karat · 10-02-2006, 04:21 PM

As far as I can tell, I'm supposed to be getting better city mileage than highway mileage for my Prius. However, I'm seeing it definitely the other way around. There are some potential explanations for bad mileage, but none of them really explain this inversion.

Specifically, I am getting 36.5 mpg in the city and ~45+ on the highway, driving at 65 mph.

Some relevant factors include:

1) The car is new. I've seen this behavior from mile 0. I've now got 3700 miles on it and I still see the same influences. Yes, both the highway and city mileage have been improving as I break the car in, but there is definitely a lag between the two.

2) Weather. Mostly I've been driving in conditions that are close to ideal, but slightly on the warm side. I have used a/c on low. I have experimented with shutting off the a/c, but with no noticable effect. However, none of my experiences have been with winter conditions yet.

3) I have observed that the engine likes to run a lot to charge the battery. In fact, I have a hard time trying to coax the car into using up the battery. The battery drains significantly when the car is parked, but the car charges it full rather quickly. From my understanding, the car is often in a state where the battery is full and will not charge any more. Thus, I am losing energy because it keeps trying to charge the battery when it is full.

4) Much of my city driving is in short 10-20 minute trips, sometimes with the car off for less than half an hour between such trips (eg work to grocerty store to home, with the car off while I am at the grocery store). I want to know if this is a strong enough factor to explain my 36.5 mpg.

Basically, point number 3 suggests that there may be a problem. Point number 4 suggests that there might not be. How can I tell? What can I do? I am going to take my car in for the 5000 mile maintainance, and I can ask them to check something out, but I don't know what to check out.

markderail · 10-02-2006, 04:36 PM

I never read anywhere that city mileage would be better than highway.
Highway driving usually means little acceleration, so to maintain constant motion requires less energy than stop and go.

The energy you get back coasting and regenerative breaking is only a tiny fraction of what was used to get up to speed. The Prius isn't a In-Wheel Electric. The In-Wheels recoup a much higher % of the energy while breaking.

What's interesting is how little driving at 55MPH, 60 or 65 makes the gas usage differ.

Makes you want to always drive at 65mph...

Beryl Octet · 10-02-2006, 04:38 PM

Your mileage sounds low to me. I don't understand the part about the battery getting low while parked. If I have green bars when I shut it down, that's what I have when I start it back up. I do notice low mileage for the first 5 or 10 minutes when the engine is cold, but in low speed (under 40MPH) stop and go, the engine is off a lot, unless it's 90 outside and a sunny day, in which case it runs more, but my city always seems higher than my highway.

Charles Suitt · 10-02-2006, 04:38 PM

<_< karat...

Your Prius is not "warmed up" or "broken in" yet. There's also a "learning curve" on how to get the best fuel economy. The Prius is a "different" car and while you can "just drive it," you can develop driving habits which will improve fuel economy. Many new Prius drivers report their best MPG results begin at somewhere between about 6,000 miles and 10,000 miles after wearing the moulding "nibs" off the new tires and limbering up the mechanical systems. Some Prius drivers believe that overfilling the motor oil can reduce fuel efficiency, and dealers frequently do overfill. Another fuel-saving technique is keeping the tire pressures higher, I run mine at 40 psi front and 38 psi rear. The 10 MPG difference between highway and in town are almost exactly what I experience after two years and 21,000 miles. Around town (mixed short and intermediate trips), I'lll do about 45 mpg, steady freeway at 65-70 MPH, I will do 52-55 MPG.

The EPS estimates are made under strictly controlled "laboratory" conditions and don't reflect "real world" driving conditions. For fun, read the language on the window decal - just below the "60 - 51" numbers.

Enjoy your technical marvel Prius, the most advanced production vehicle available.

Beryl Octet · 10-02-2006, 04:41 PM

<div class='quotetop'>QUOTE(Mark Derail @ Oct 2 2006, 04:36 PM) [snapback]327102[/snapback]</div>

Quote:

I never read anywhere that city mileage would be better than highway.

[/b]

It is EPA rated at something like 60 city, and 51 Highway.

I see around 50 on the highway, and 55 on my commute, or better, depending on the amount of stop and go and the weather (AC usage). I've seen 70 MPG on some trips, but that's with a traffic tie up and lots of stop and go, and very little over 40MPH. The engine runs just enough to charge the battery, then the car stays in electric mode until the battery droops.

ditto231 · 10-02-2006, 04:46 PM

Your problem could be number 4. You said short trips 10 to 20 minutes, the 1st 5 minute I only got about 25 to 30mpg. The next 5 minutes about 30-40mpg, but 10 minutes and if I pulse and glide in the city I should get about 60 to 75 mpg.

karat · 10-02-2006, 05:16 PM

Okay. The three Prius owners I've talked to in person all have better city mileage than highway mileage. All three thought it was strange that I was seeing worse city than highway mileage. It was suggested that I post here for wider opinions.

I'm aware of the break-in period, but I should have started to see somewhat better mileage by now. Also, most sources do not want to provide numbers. If I can get something more specific than "it's not as good during the breakin period," that would be helpful in setting realistic expectations.

As for learning curves, I've read driving guides on how to get the most mileage on the Prius. It really feels like they are talking about a different car. (Well, they are talking about a 2005, not a 2006, so technically they are. I don't know if much has changed.) I certainly don't see "warp stealth." Sometimes at low speeds, I can feather the accelerator and convince the engine to coast. My biggest frustration in the car is trying to convince it to neither run the gas motor nor recharge the battery that is already full. Electric engine only mode lasts for about 30 seconds before it tries to recharge the battery. If I try to coast, it slows down the car appreciably while failing to recharge the battery.

It's hard to tell what I should be learning to do. ("Read a guide" and "maximize the mpg meter" are not sufficient, as I've attempted both.)

However, the original question is "Is 36.5 mpg in the city while I'm getting 45-50 on the highway at 65+ mph reasonable for my situation, or is there a potential problem? If there is a potential problem, what can I check to prove/disprove this?"

**Tideland Prius** · 10-02-2006, 05:34 PM

<div class='quotetop'>QUOTE(Mark Derail @ Oct 2 2006, 01:36 PM) [snapback]327102[/snapback]</div>

Quote:

I never read anywhere that city mileage would be better than highway.
Highway driving usually means little acceleration, so to maintain constant motion requires less energy than stop and go.

The energy you get back coasting and regenerative breaking is only a tiny fraction of what was used to get up to speed. The Prius isn't a In-Wheel Electric. The In-Wheels recoup a much higher % of the energy while breaking.

What's interesting is how little driving at 55MPH, 60 or 65 makes the gas usage differ.

Makes you want to always drive at 65mph...
[/b]

It's rated 4.0/4.2L/100km according to Transport Canada. I'm probably one of the rare few that gets city > highway mileage. I average 4.4L/100km over the summer while on the highway (usually to the States), it's 5.0L/100km at 70mph.

<div class='quotetop'>QUOTE(karat @ Oct 2 2006, 02:16 PM) [snapback]327132[/snapback]</div>

Quote:

Okay. The three Prius owners I've talked to in person all have better city mileage than highway mileage. All three thought it was strange that I was seeing worse city than highway mileage. It was suggested that I post here for wider opinions.

I'm aware of the break-in period, but I should have started to see somewhat better mileage by now. Also, most sources do not want to provide numbers. If I can get something more specific than "it's not as good during the breakin period," that would be helpful in setting realistic expectations.

As for learning curves, I've read driving guides on how to get the most mileage on the Prius. It really feels like they are talking about a different car. (Well, they are talking about a 2005, not a 2006, so technically they are. I don't know if much has changed.) I certainly don't see "warp stealth." Sometimes at low speeds, I can feather the accelerator and convince the engine to coast. My biggest frustration in the car is trying to convince it to neither run the gas motor nor recharge the battery that is already full. Electric engine only mode lasts for about 30 seconds before it tries to recharge the battery. If I try to coast, it slows down the car appreciably while failing to recharge the battery.

It's hard to tell what I should be learning to do. ("Read a guide" and "maximize the mpg meter" are not sufficient, as I've attempted both.)

However, the original question is "Is 36.5 mpg in the city while I'm getting 45-50 on the highway at 65+ mph reasonable for my situation, or is there a potential problem? If there is a potential problem, what can I check to prove/disprove this?"
[/b]

#3 concerns me. Why would the battery drain while parked? It should be exactly the same level as you left it before you shut off (unless it's on the borderline between two levels). Are you trying to use the battery? If so, that might explain the low mpg. Using the battery in EV mode means the battery will drain and if the battery drains, the engine will recharge and bump it back up to 6 bars. Try to use the engine more often and not the battery. It sounds counterintuitive but you will get better mileage.

Take note the difference between coasting and gliding. What we call "coasting" is when the accelerator pedal is NOT depressed and the electric motors are recharging the battery via regenerative braking (green arrows to the battery). "Gliding" is when the engine is off and there's no arrows to or from the battery.

chimohio · 10-02-2006, 05:49 PM

I've got just slightly under 2000 miles on mine and also see lower mileage in town, mostly suspected to be due to not yet broken in and definitely shorter trips. Fremont OH is a relatively small town and it doesn't take long to go from place to place so much of my in town driving is short (10 - 20 minutes) but I don't see any where near the 60 - 70 - this gives me something to strive for. I probably average about 45 mpg in town, and have been averaging 50 on longer drives to work. Have not noticed any battery issues.

Beryl Octet · 10-03-2006, 08:53 AM

<div class='quotetop'>QUOTE(karat @ Oct 2 2006, 05:16 PM) [snapback]327132[/snapback]</div>

Quote:

Okay. The three Prius owners I've talked to in person all have better city mileage than highway mileage. All three thought it was strange that I was seeing worse city than highway mileage. It was suggested that I post here for wider opinions.

I'm aware of the break-in period, but I should have started to see somewhat better mileage by now. Also, most sources do not want to provide numbers. If I can get something more specific than "it's not as good during the breakin period," that would be helpful in setting realistic expectations.

As for learning curves, I've read driving guides on how to get the most mileage on the Prius. It really feels like they are talking about a different car. (Well, they are talking about a 2005, not a 2006, so technically they are. I don't know if much has changed.) I certainly don't see "warp stealth." Sometimes at low speeds, I can feather the accelerator and convince the engine to coast. My biggest frustration in the car is trying to convince it to neither run the gas motor nor recharge the battery that is already full. Electric engine only mode lasts for about 30 seconds before it tries to recharge the battery. If I try to coast, it slows down the car appreciably while failing to recharge the battery.

It's hard to tell what I should be learning to do. ("Read a guide" and "maximize the mpg meter" are not sufficient, as I've attempted both.)

However, the original question is "Is 36.5 mpg in the city while I'm getting 45-50 on the highway at 65+ mph reasonable for my situation, or is there a potential problem? If there is a potential problem, what can I check to prove/disprove this?"
[/b]

You're not driving in "B" instead of "D" or anything like that? "B" stands for engine braking, and some people reportedly think it means "Battery" or something...

Tire pressure OK? I had a slow leak, and was driving around with 25 lbs or so, and noticed a mileage drop.

I can't remember exactly when my mileage got better, but I thought I was seeing in the 50's after 2500 miles or so. I know the first 1000, I never got above mid 40's for the most part. I'd expect to see much better mileage that what you are getting, especially on the city part, assuming you are not trying to recreate the Fast and the Furious from stoplight to stoplight or something like that. Could be your trips are just short enough that the engine never fully warms up, I suppose, but if you can go for a longer city drive and see what you see on the "consumption" dispaly after 15 minutes or so of city driving. I'm assuming these are the same between an '05 and an '06. I know that for my stop and go commute, it doesn't hit the plateau until about 10 or 15 minutes in. The first 5 minutes is like in the 20's, then the next in the 30's and then it levels off in the 50's.

The part about the battery level dropping while parked, i.e., I assume with the car off, definitely sounds like a problem. I'd note that for when you talk to your service dept., that should not be happening, but without seeing the displays, it's hard to say what you are seeing.

Beyond that, and I think I know a lot about cars, not sure what else could be be wrong, or even what the average person could really check even if someone had an idea. It's a new car, it's under warranty, call your dealer's service dept. and have them check it out.

10-02-2006, 04:36 PM	#2
markderail 4-Seasons Driver Join Date: Sep 2006 Location: Pierrefonds (Montreal) Quebec Canada Posts: 1,675 My Car: 2006 Prius Model: Package: B Thanks: 97 Thanked 21 Times in 17 Posts Friends: 8	I never read anywhere that city mileage would be better than highway. Highway driving usually means little acceleration, so to maintain constant motion requires less energy than stop and go. The energy you get back coasting and regenerative breaking is only a tiny fraction of what was used to get up to speed. The Prius isn't a In-Wheel Electric. The In-Wheels recoup a much higher % of the energy while breaking. What's interesting is how little driving at 55MPH, 60 or 65 makes the gas usage differ. Makes you want to always drive at 65mph... __________________ Don't play the new boring forum game, Most Boring Thread...

10-02-2006, 04:38 PM	#4
Charles Suitt Senior Member Join Date: Oct 2004 Location: Dallas TX Posts: 1,624 My Car: 2007 Prius Model: Package: #6 Touring Thanks: 0 Thanked 1 Time in 1 Post Friends: 0	<_< karat... Your Prius is not "warmed up" or "broken in" yet. There's also a "learning curve" on how to get the best fuel economy. The Prius is a "different" car and while you can "just drive it," you can develop driving habits which will improve fuel economy. Many new Prius drivers report their best MPG results begin at somewhere between about 6,000 miles and 10,000 miles after wearing the moulding "nibs" off the new tires and limbering up the mechanical systems. Some Prius drivers believe that overfilling the motor oil can reduce fuel efficiency, and dealers frequently do overfill. Another fuel-saving technique is keeping the tire pressures higher, I run mine at 40 psi front and 38 psi rear. The 10 MPG difference between highway and in town are almost exactly what I experience after two years and 21,000 miles. Around town (mixed short and intermediate trips), I'lll do about 45 mpg, steady freeway at 65-70 MPH, I will do 52-55 MPG. The EPS estimates are made under strictly controlled "laboratory" conditions and don't reflect "real world" driving conditions. For fun, read the language on the window decal - just below the "60 - 51" numbers. Enjoy your technical marvel Prius, the most advanced production vehicle available. __________________ Charles Suitt Dallas Texas 2007 Touring Edition (Former Prius: 2004)

10-02-2006, 05:49 PM	#9
chimohio Senior Member Join Date: Sep 2006 Posts: 460 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I've got just slightly under 2000 miles on mine and also see lower mileage in town, mostly suspected to be due to not yet broken in and definitely shorter trips. Fremont OH is a relatively small town and it doesn't take long to go from place to place so much of my in town driving is short (10 - 20 minutes) but I don't see any where near the 60 - 70 - this gives me something to strive for. I probably average about 45 mpg in town, and have been averaging 50 on longer drives to work. Have not noticed any battery issues. __________________ Where no car has gone before! Reverse beeper disabled, rear bumper protector, MFD hood, block heater, OEM all weather floor mats. BT stiffener brace, mud flaps, Goodyear ComfortTred 195/60/15.

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10-02-2006, 04:21 PM	#1
karat Join Date: Sep 2006 Posts: 12 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	As far as I can tell, I'm supposed to be getting better city mileage than highway mileage for my Prius. However, I'm seeing it definitely the other way around. There are some potential explanations for bad mileage, but none of them really explain this inversion. Specifically, I am getting 36.5 mpg in the city and ~45+ on the highway, driving at 65 mph. Some relevant factors include: 1) The car is new. I've seen this behavior from mile 0. I've now got 3700 miles on it and I still see the same influences. Yes, both the highway and city mileage have been improving as I break the car in, but there is definitely a lag between the two. 2) Weather. Mostly I've been driving in conditions that are close to ideal, but slightly on the warm side. I have used a/c on low. I have experimented with shutting off the a/c, but with no noticable effect. However, none of my experiences have been with winter conditions yet. 3) I have observed that the engine likes to run a lot to charge the battery. In fact, I have a hard time trying to coax the car into using up the battery. The battery drains significantly when the car is parked, but the car charges it full rather quickly. From my understanding, the car is often in a state where the battery is full and will not charge any more. Thus, I am losing energy because it keeps trying to charge the battery when it is full. 4) Much of my city driving is in short 10-20 minute trips, sometimes with the car off for less than half an hour between such trips (eg work to grocerty store to home, with the car off while I am at the grocery store). I want to know if this is a strong enough factor to explain my 36.5 mpg. Basically, point number 3 suggests that there may be a problem. Point number 4 suggests that there might not be. How can I tell? What can I do? I am going to take my car in for the 5000 mile maintainance, and I can ask them to check something out, but I don't know what to check out.

10-02-2006, 04:38 PM	#3
Beryl Octet Senior Member Join Date: Aug 2006 Location: Abingdon VA Posts: 1,294 My Car: 2005 Prius Model: Package: #4 Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Your mileage sounds low to me. I don't understand the part about the battery getting low while parked. If I have green bars when I shut it down, that's what I have when I start it back up. I do notice low mileage for the first 5 or 10 minutes when the engine is cold, but in low speed (under 40MPH) stop and go, the engine is off a lot, unless it's 90 outside and a sunny day, in which case it runs more, but my city always seems higher than my highway.

10-02-2006, 04:46 PM	#6
ditto231 Join Date: Jun 2006 Posts: 65 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Your problem could be number 4. You said short trips 10 to 20 minutes, the 1st 5 minute I only got about 25 to 30mpg. The next 5 minutes about 30-40mpg, but 10 minutes and if I pulse and glide in the city I should get about 60 to 75 mpg.

10-02-2006, 05:16 PM	#7
karat Join Date: Sep 2006 Posts: 12 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Okay. The three Prius owners I've talked to in person all have better city mileage than highway mileage. All three thought it was strange that I was seeing worse city than highway mileage. It was suggested that I post here for wider opinions. I'm aware of the break-in period, but I should have started to see somewhat better mileage by now. Also, most sources do not want to provide numbers. If I can get something more specific than "it's not as good during the breakin period," that would be helpful in setting realistic expectations. As for learning curves, I've read driving guides on how to get the most mileage on the Prius. It really feels like they are talking about a different car. (Well, they are talking about a 2005, not a 2006, so technically they are. I don't know if much has changed.) I certainly don't see "warp stealth." Sometimes at low speeds, I can feather the accelerator and convince the engine to coast. My biggest frustration in the car is trying to convince it to neither run the gas motor nor recharge the battery that is already full. Electric engine only mode lasts for about 30 seconds before it tries to recharge the battery. If I try to coast, it slows down the car appreciably while failing to recharge the battery. It's hard to tell what I should be learning to do. ("Read a guide" and "maximize the mpg meter" are not sufficient, as I've attempted both.) However, the original question is "Is 36.5 mpg in the city while I'm getting 45-50 on the highway at 65+ mph reasonable for my situation, or is there a potential problem? If there is a potential problem, what can I check to prove/disprove this?"