Same Prius, Not The Same MPG

OK. I'm curious, what type of readings are out of line on coolant temperature, or other things that might indicate start up of the hybrid system are not acting correctly.

I didn't mean to offend at all. After reading some of the responses, it seemed that perhaps something is wrong with my car, particularly with mpg during its start up phase. It seems to work great once it is initially up and running, both highway and city. Since the OP hadn't yet found out what was going on in his car versus his sisters, I thought there might be some things to look for on my system.

Millage seems to have dropped instead of going up as temperatures have gotten hotter. I am not upset with the mileage that I am getting. I was surprised with the size of the start up penalty when I first started reading the the forum. If there is something wrong with my car I'd like to get it fixed quickly though, and was hoping for testing, diagnosis suggestions.

 

doesnt sound like your car has issues. u got 55 mpg on trip back which demonstrates that you can get good mileage. your tank average being as low as it is simply means that those short trips do take a toll.

keep that mind when u take those short trips. experiment with different driving techniques. start one, stick with it for at least a week before evaluating its effectiveness. too many variations due to traffic to make any conclusions in less time. my mindset; maintain as constant a speed as you can, which in town pretty much means AVOID BRAKES AT ALL TIMES... which is #1 rule right after "dont hit anything".

if you see a light that is red 2 blocks ahead and you can see there will be a half dozen cars sitting there, start coasting. so what if people behind u dont like it. they are doing nothing but increasing the amount of standstill time at the light anyway. racing from light to light is what kills your mileage.

i do it every day and will piss off someone...that much is a given. but generally after they have roared around me burning up about ¼ gallon of gas in the process, i will frequently see them 3-7 cars ahead of me 10 minutes later... so let them, they arent really going anywhere and trust me on this, only a very small portion of their road rage is directed at you because as soon as they pass u, u r out of their mind and they are once again, PO'd at the new car ahead of them

 

Short diagnosis in approximate decreasing order of significance:
- Short trips kill MPGs in all cars. Walk or bicycle when possible.
- Drive so as to *minimize* the use of the battery, not maximize. Energy conversions into and out of batteries unavoidably waste energy. You are correct to avoid braking, but you should accelerate briskly because this maximizes the efficiency of the engine. Ideally one would rapidly accelerate up to some maximum speed, then glide all the way to the next stop, but obviously this is usually not practical.
- Higher tire pressures increase MPGs. You can safely go up to the maximum pressure shown on the side of the tire when measured "cold" (cold = driven no more than one mile in the previous hour; the pressure increase which occurs in a hot tire is accounted for in the "cold" rating and measurement, so do not bother to measure a hot tire). The ride will be harder and the handling will change.
- Grossly overfilled oil can immediately reduce MPGs. Slightly overfilled oil can gradually reduce MPGs by fouling the MAF (mass airflow sensor), which confuses the engine computer. (MPGs or not, *always* check the oil yourself before driving away from *every* oil change. Everyone makes mistakes; oil change mistakes can quickly become extremely expensive.)

 

I understand that short trips and more braking can kill mpg in a normal car, but I don't think it does to a great extent in the Prius.
All my journeys, exept one, in my first tankfull were of 3 miles or less 75% of them from a cold engine and I achieve 57.2 uk mpg (divide by 1.2 = 47.7 US mpg). I use EV from the off, travelling at 19mph out of the minor urban roads until the battery runs too low (2 bars) or I reach the main urban road (~0.5 miles) and increase speed to the traffic (40mph). I'm then on ICE travelling 40-50mph for 2 miles with two roundabout stops, I use light regenerative braking to charge the battery when slowing, down rather than slow down earlier, to keep pace with the traffic. I'm then back to a minor urban road, by which time the battery has recharged to 7 bars, there are speed humps which give me a perfect excuse to slow to 19mph again and induce EV automatically, this takes me 0.5 miles to the end of my journey. A similar driving pattern to go home and back for lunch and on my return home at the end of the day keeps my mpg at 57.2 UK.
The warmed ICE journey (25% of my mileage) is the one on the way back after lunch.
I'm only a new Prius owner but I find that using EV at the start and end of a journey, positive accelleration (but not brisk) and light regenerative braking rather than gentle deccelleration work best for me.
All of the above is in NORMAL mode with the occasional PWR mode to join the traffic on the main road and the roundabouts. I don't use ECO mode, it's too depressing.

 

2010 Prius mpg situation.

We have two cars, both exactly the same except for the color. Both are II models. The first one was purchased the day they were introduced and it has a 16,000 mile average of just over 51 mpg. The second was purchased in December, it has the same total miles on it; it has a lifetime mpg of just over 55 mpg. Why?

Both my wife and I drive both cars and we switch at the beginning of each month to keep the total miles somewhat equal. Obviously we have differing driving habits but the mpg for both cars remains as stated. The newer one is always 10% better than the older one.

Tire pressure is the same on both, they both have the same brand of tires, oil was changed at the same time on both, wieght onboard is somewhat equal no matter who drives either car. The dealer cannot explain the difference. Can anyone tell me why one is better on fuel than the other one?

Obviously the miles on the #2 car were accumulated at a quicker rate than that of the #1 car but now they are somewhat equal. Could the rate at which #2 accumulated the miles make a 10% difference.

Obviously they make mid year corrections and improvements but could the 7 months difference in build dates make theat much difference?

I am baffled. Can anyone explain?

 

Assuming tyre pressures are the same, I would check wheel alignment in this case.

 

Out of curiosity, how you are determining these lifetime mileage figures? Is it from manual calculations or based upon the trip computer/FCD? If it's the latter, I would've expected the newer one to read lower mileage.

Perhaps a little bit of it is from now having learned how to drive the Prius for efficiency?

 

I did because I wanted to monitor some of our NHW11 metrics. However, they have yet to release the ZVW30 codes so I don't think it is needed.

Bob Wilson

 

With these four metrics, we will have metrics to determine:

• engine warm-up profile - this can vary
• engine rpm - maps to energy requested for driving conditions
• MAF - fuel consumptions
• speed - distance and driving profile

With metrics, we can form testable hypothesis and see if something can be done. We can even attempt to replicate the driving profile. But without out them, these are just words, suggestions.

Bob Wilson

 

OK, so I checked and it was very hard to read the oil level for some reason. Perhaps because the oil is such a light color.

I removed the dipstick, wiped, inserted and removed about 5 times until I could finally discern that the oil level is quite a bit higher than the higher of the two bumps on the dipstick.

So could this be affecting my mileage? What should be done about it -- go to the dealer and have them drain 1/2 quart or is there an easier way?

I was driving my friend's 2007 Prius yesterday and he lives near where I live and gets 47 MPG average, so I really do think something's wrong.

 

Yes, excess oil can affect your mileage negatively. Have whoever it is that changed your oil remove the extra oil.

You could try to siphon it out w/a siphon pump, but I personally had trouble w/the one I bought and it took me a long time. (I had to do that because the dealer that changed oil that time was already 350 miles away and I wasn't going back there anytime soon.)

As for that friend, it's an apples to oranges comparison. We know nothing about the length and type of drives they do, how similar their routes are, how they're driving their Prius, their tire pressures, whether they leave their car running (w/the ICE running) for 2-3 mins after power on, etc. All of the above make a difference.

With 2-6 mile drives, almost all city w/traffic lights and stop signs, in non-flat terrain, I don't think you're going to get 47 mpg, at least not easily.

Remove your excess oil, inflate your tires closer to sidewall max then tell us the mileage you get when driving w/a warmed up engine for a segment of highway for at least 5 mins in each direction at a steady speed (say 65 mph) using cruise control. Do it in both directions to help cancel out effects of wind and elevation change and when there's light or no traffic. At least we'd have somewhat of a baseline we can talk about and compare w/others.

 

Celtic Blue said: Good, one item checked off.

Doesn't mean anything. They don't drive the same because yours doesn't glide well. Have the alignment checked (you get a free one in the first year.)

We've had our 2010 just almost a year now. Where can I get this free alignment??
Thanks,
radio

 

If you've dipped the stick 5 times you will have dragged some oil up the dipstick tube and will get a false high reading as the stick is picking up oil from the tube.
The best method is to check it when the vehicle has been parked for a while, pull out the stick, wipe it clean then dip and pull out once.
Ideally you could take out the dipstick while the engine is warm and wipe it, leave the car parked for a while (with the stick out), then dip and pull out and check.

 

I found out that using BP or sheetz gas around here (pa) I get avg 45 mpg, whereas, using a local gas station i easily get 55 constantly.

 

No, because I brought it in to the dealer and they confirmed that it was overfilled and drained some oil at no charge.

So far I'm not sure if this has affected the mileage, but I don't think it has.

 

10mpg???????:jaw:

 

Hi. I have a Gen III with just a bit over 3000 miles on it. My gas mileage has been dropping steadily since I bought the car. When I first got it I was getting about 45 mpg in combined driving. Since then each successive tankful has shown less mpg. I just filled the tank and the gauge is showing about 33.5.

I also noticed that the battery rarely goes above 2-3 bars (unless I'm driving on the highway). I suspect the car is running on the gas engine most of the time causing the low mpg.

Has anyone experienced a similar problem? Is there something I'm doing wrong in the way I drive? Help! I'm getting ready to take it back to the dealer and see if they can find a problem.

Thanks.

 

I'll say it again. Please start a new thread w/answers to the questions at http://priuschat.com/forums/gen-iii...-answer-these-questions-esp-if-youre-new.html. We have insufficient info, at this point.

 

That could be a lot of crank case pressure depending on how much it was overfilled. Possibly lowering mpg.

 

Which local gas are you using? I used to like Sunoco, however, the mileage has dropped and now it does better with Wawa. Yes, I believe 10 MPG with different gas!
Bob