Same Prius, Not The Same MPG

This is a very good idea. Once you have an idea if it is drag or propulsion you can narrow down the search for the cause/difference. Cutting the potential source of problems in half is a good start.

Is there some "learning" to the ECU? I've read before in GII's that they sometimes came back from service acting funny. Disconnecting the 12V for a time then reconnecting was sometimes a fix...sort of a hard reboot.

Any chance that the throttle pedal sensor could be out of adjustment and keeping the ICE on when it shouldn't?

Dealers of any make have a pretty hard time of diagnosing this sort of problem unless you can narrow it down for them.

 

I'm a new owner too,live in Florida where the roads are excellent and no hills to speak of,so therefore I should get
good mileage.Well,I've done two fillups so far and the results have exceeded my expectations.My first measurement was
done driving about 90% highway(speed betwen 55 mph and
68 mph) and 10% city mostly in ECO mode and using on the HWY
cruise control a lot. 402 miles 7.5 gallons 53.6 mpg.My second measurement was done 70% HWY driving between 55 mph and 58 mph,30% in moving traffic.335 miles 5.8 gallons
for 57.7 mpg.Therefore,it is my opinion that if you are driving
in ECO mode most of the time and you don't have a lead foot,you should be doing a lot better in city driving.Driving in
the city would increase the use of the electric motor up to
40 mph,thus cutting back on fuel consumption.However,if
you floor the accelerator a lot,you will lose mpg.In summary,
if you drive like an old lady in the city,you should get a lot
better mileage.Check out pages 192-194 in your manual.
Try to drive in the hybrid zone after initial acceleration while
in the city.Good luck.

 

Excellent!!! You have done exactly what is needed:

• hill roll down test - both vehicle achieve the same speed
• hill climb test - perception of less power!

Ahhh, I would not stand in the way of a Lexus upgrade ...

If you want to continue diagnosis of your 2010 Prius, let me know. I have this 'hill climb' data we can use to test your Prius:

This was a climb of a 1.2 mile long, 525 ft. high hill. If you can find a reasonably close hill climb route, we can compare your climb fuel consumption to mine. This would quantify how poorly your engine is working. Then comes the fun part ... isolating the problem:

• ignition
• variable valve advance
• EGR subsystem
• . . .

Just for grins, when was your engine oil changed? Do you have the receipt that might indicate the brand and weight used? How does the oil look on the dip-stick? Does it have an unusual odor? Where does it sit relative to the "F" mark?

The last question is especially important since the 2010 Maintenance Manual explicitly states it must not be above the "F" mark.

Other hypothesis:

• defective thermostat - this could lead to the coolant being too cool and the engine always trying to run to warm it up. Big MPG impact here and there would be no error code.
• defective exhaust coolant warming valve - there is a valve that operates to give straight pass once the car is warmed up. If the valve is stuck or the car thinks it has not warmed up enough, it becomes a constriction ... back-flow limit ... on the engine.
• defective muffler bypass valve - at high power settings, it opens to reduce back-pressure. If it does not open, high power performance would be impacted.

But I also understand if spending time trying to diagnose this car is not something you're interested in pursuing. Still, I'm game if you are.

Do you have an independent mechanic you trust? We're talking someone who actually knows what a VOM and real test instruments are? . . . Too bad you're not in Frisco, there are two really excellent independent shops: Art's Automotive and 'Luscious Garage' (sp?).

Bob Wilson

 

Can you try a different service department? Something can't be right. You have something(your sister's car) to compare with.

--Mickey

 

Bob,

do you think that a Scangauge would help him diagnose the problem? He could easily try it on his and his sisters cars, comparing such values as coolant temp, ICE RPM, ignition settings, etc. Some of those results might help you help him.

Dark Prius,

Dianne Whitmire, Fleet Sales Director at Manhattan Beach Toyota, has been very active on this forum. She is not a service person but knows a lot and has been helpful to PriusChat members. Her numbers are: 310 939 7801 office, 949 689 0717 cel. She might have some ideas.

 

I've read enough of this thread to think that Dark Prius has a Gen III with some kind of defect. Unfortunately, he has been unable to get resolution through his dealership.

My suggestion would be to dress in your best suit, and go to the "other" nearest Toyota dealership and ask to speak with the service manager. Explain in your best english, very politely, the issue you are having with your car and the diff. driving your sisters and yours on the same route. Bring up the possibilities that Bob suggested. You'll get this resolved. It is something simple, you just need to get the manager on your side believing that there is something wrong here even before the tech starts digging! Rememember to suggest that if they fix it, you'll be taking the remainder of your business to them!

 

Any instrumentation would help. I don't have a scangauge but these data points would help.

This is also one of the cases were Volume I of the maintenance manual with the scangauge would help with some of the vehicle specifications. But I started with Volume II because I'm more interested in the parts, the subsystems. But I don't get the impression the owner shares our interest in the gear-head aspects of the car. However, I agree that finding another, clueful dealer, would help.

This car has not 'thrown a code' (or has and there is no 'check engine light') and trying another service center is a good option. I get the impression that some dealer service centers may be more into 'follow the book' rather than thinking about vehicle systems. However, the local Huntsville service center revealed the throttle plate cleaning to solve a failure to start problem. We've also had reports of other service centers with stellar support. A Toyota service center also keeps any repair within the warranty range.

This is one of those cases where Art's Automotive or Luscious Garage | Hybrid Specialists may make sense. Independent, shops have impressed me with their ability to 'think outside the box.' But this is a new car and a phone call first makes sense to see if they would look at the car.

Bob Wilson

 

have been tracking my commutes to work. its 7 miles one way. residential streets 9% @ 25 mph. 54% @ 40 mph, and 37% @ 35 mph (per google maps)

mileage is 8-12 mpg less in morning. morning commutes, temps mid 40's, lights on. minimal traffic. worst commute;


6.9 miles 50.9 mpg, OAT 45º, avg speed 33 mph. lights on, heat on set to 72º

now, with all other things reasonably equal except heat, other morning trips avg 53- 55 mpg.

the "heat" penalty is interesting and will be drivng the Pri for next few weeks before any drastic change in weather to see if this result is repeatable since have only used heat once (after that 50 mpg tank, that scared me!! but will sacrifice for science)

for reference, afternoon trips temps running between upper 60's and lower 80's (supposed to be 90 today, but no work today, so oh well) average speed much lower between 20 -28 mph (morning commutes run 32 or 33 mph) but worst afternoon trip is 62 mpg. mostly from starting out much warmer im guessing

will be posting full stats probably separate post. after i collect data for grill blocking etc. want to get at least 3-4 examples of each

 

I still think this is a battery charge issue.

I would take your 12 volt out and have it tested at an autoparts store. Advanced and NAPA have worked for me. This will also cause a hard reboot of all the computers in the car. If you do this give it a few days to relearn the control settings.

What we really need to know is the main battery state of charge and when and how much current is coming and going to it.

Hear is an idea. Take your sisters car and 2 foot it ie. brake and gas at same time. Will this induce added regen drag? Similar to what you are experiencing in your car? Something I haven't seen talked about on the forums for years, maybe gen 1. Maybe a brake sensor thinks your riding the brakes?

 

I think your probably right, but I don't think it's a 12V batt issue. If I remember correctly he is getting decent highway mileage, it's city mileage that is bad. At steady state speed above 46 MPH, I think the hybrid system is used very little, I think your mostly ICE at higher speeds, it low speeds that I think the hybrid system comes into it's own, and it's low speeds that his mileage suffers. It could be as simple and hard to find as a loose ground

 

I haven't tested it as much as Dark Prius has, but my mom's 2010 Prius IV is getting mid 40s for MPG. The car seems much heavier than my 2006 Prius. I tried driving it and seeing if I could get better mileage, but only got slightly better (but with 4 people in the car) when I drove it. I get just above or below 50 in my 2006.

Dark Prius - what are the production dates of you and your sister's prius? Just curious.

 

Looking at the cars VIN number, from the right look for the number right after the letter A, is it a 0 or 5 on your sisters and your Prius.

A?xxxxxx

Wayne

 

Just for grins, when was your engine oil changed? Do you have the receipt that might indicate the brand and weight used? How does the oil look on the dip-stick? Does it have an unusual odor? Where does it sit relative to the "F" mark?

The last question is especially important since the 2010 Maintenance Manual explicitly states it must not be above the "F" mark.

Other hypothesis:

• defective thermostat - this could lead to the coolant being too cool and the engine always trying to run to warm it up. Big MPG impact here and there would be no error code.
• defective exhaust coolant warming valve - there is a valve that operates to give straight pass once the car is warmed up. If the valve is stuck or the car thinks it has not warmed up enough, it becomes a constriction ... back-flow limit ... on the engine.
• defective muffler bypass valve - at high power settings, it opens to reduce back-pressure. If it does not open, high power performance would be impacted.

But I also understand if spending time trying to diagnose this car is not something you're interested in pursuing. Still, I'm game if you are.

Do you have an independent mechanic you trust? We're talking someone who actually knows what a VOM and real test instruments are? . . . Too bad you're not in Frisco, there are two really excellent independent shops: Art's Automotive and 'Luscious Garage' (sp?).

Bob Wilson[/quote]

Bob,
I have not been reading posts for a while and just found this one. I should probably read to the end to see if it was answered. We have a 2010 V w atp and about 3,200 miles on it. Similar symptoms. It gets 50 to 52 MPG on highway trips, 40 to 42 city. The city milage is getting worse. I have an Actron scan tool and know how to use it. I am interested in answering the mileage question prior to the 5K trip to the dealer. I doubt they have the skills to fix it.
Bob

 

WOW. we are all very meticulous in our own ways.

cheers for the prius owners. we truly are a bit different.

 

What does this signal?

Bob Wilson

 

Just checking to see which plant produced the particular Prius. I have talked to owners and seen a few Prius from the plant code 5 which have had some sloppy assembly compared to others from plant code 0. Just tying up what might be a loose end in explaining some things.

Wayne

 

I know tons of suggestions are overwhelming... especially when they are tedious, time consuming and redundant.

1. At least check the oil level to make sure your not overfilled. Hwy speeds could be less sensitive to the overfilling. For best mileage, most prius owners recommend about One quarter inch below the fill mark, but this should not be near as big as issue as your reflecting. A whole quart overfill could be serious.

2. I assume you both have your cars set on the same driving mode?.. Eco, verses normal, verses power? When driving in Eco mode, it will "feel" like you have less power because it takes more movement of the pedal to get the car going. However, you should be getting pretty good mileage in that mode if the readout is accurate.

3. Are you getting gas a different places?

Since they coast the same I would think there are no drag issues.

4. One more thought, have you tested your true gas mileage at the pump to rule out if the dash mileage readout is just lying to you and maybe miscalibrated?... Would be funny if your getting the same mileage and dont know it!

I bet if you get the backing of Toyota to trade it in without penalties due to the dealer not being able to find the issue, the dealer would have motivation to look harder.

 

Did you ever find a cause for this? I have a 2006 and 2010 Prius. My brother has a 2010. I always got close to 60mpg with the 2006 until the first tire change, but still get 54-55 (except winter). If I try real hard with the 2010 I can get about 57, but mostly I average 53-54mpg because "I just have to pass one more". My brother is getting 42, although he does drive faster on the highway. All of these mpg ratings are by the computer, and actual is 1-2 mpg lower. I think 42 (40 actual) is way too low. If I really try hard and work at it, I can get mine down to 48-49, but as soon as I start driving like a sane person again it goes right back up. I think there is something wrong with his. Any suggestions for him? Thanks.

 

I forgot to mention, my 2010 has about 3500 miles, and my brother's around 2500.