Same Prius, Not The Same MPG

I've gotten to where I like power mode most of the time... yes I don't get the "best" gas mileage, but its not much difference. I like the feel of power and the punch.. the pedal is much more siensitive which I like.
I still get about 46 - 49mph while being mindless about it.

I think I've driven prius's long enough that my subconscious habits give me decent gas mileage still.

I don't recommend power mode for new drivers... eco is a good learning tutor to get a feel for what works best... turning off eco or going to power applies all the same rules and habits.. just much more sensitive and takes more skill with the foot pedal.

Just takes a little time.

Even in power mode I can still drive in such a way to get 53 - 55mph but if I'm gonna drive that mushy, I might was well be in normal mode or even eco.

I've said this before.... put this same software in any car and you will greatly improve the gas mileage.....as it teaches people how to work with the car and physics rather than against it.

 

One more suggestion, do you carry any weight in your trunk ?
(compared to your sister's car)
More weight means more work for the engine uphill.

 

You need to wax your front bumper and hood. All kidding aside, read every post and am now subscribed. Interesting issue that I don't have, but have interest.

 

One earlier post asked about tires.

If I'm not mistaken, there may be three different "OEM" tires on the 2010 Prius. One of them, the Bridgestone Ectopia EC20 is said to have been discontinued by Bridgestone (per Discount Tire, which is getting me one from an out-of-state store to use as my full size spare.

So ... do the tires match? (Pardon if already answered. Read all the posts, but there was a lot of info to absorb).

If different, it's one avenue we can explore for comparative rolling resistance.

 

I have a 2010 Prius II and I get 36 MPG in the city using Eco mode.

I posted about this before and people seemed to think it was normal, but here people are saying that 40MPG using normal mode is low enough that something is wrong with the car.

What's more likely? Is it likely there's something wrong with my car too that's producing these lower mileage figures?

 

We need empirical data:

AutoEnginuity® - OBD2 Scan Tool - Professional PC and PDA Diagnostics - $250 and your laptop
​

If you have a Windows laptop, you could use this scanner to record the data needed to determine what is going on:

By recording:

• engine coolant temperature
• velocity
• MAF flow
• air pressure

We can analyze your vehicle performance and see what is going on. Then we can make effective suggestions that can be verified by subsequent data sessions.

Bob Wilson

 

if you drive the car moderately, it is likely there is something wrong with the car. i don't that's in a gen II.

 

After reading this thread I'm wondering if something is wrong with my car too. Let me know if its just my routes or if there is something to check out.

Yesterday I had a 39 mile trip, 19.5 miles each way. It was 93 degrees on the way out. I was reading 28mpg at 3 miles, 34 at 5 miles, and 46.3 total on the way out. On the way back it was 85 degrees, total trip 50.4 indicated. I calculate that means 55.3 on the way back. 12 miles 65mph highway with varying speeds 60-70, 7 miles of 45mph road with a few lights, the rest 25mph roads with stops signs. It was cooler with less traffic on the way back. Should my start up milage be like this. Indicated is about 2 mpg above actual on a tank. I have lots of short trips and they seem to greatly reduce my average. My trip out was in eco mode, back in pwr. My tank average is at 41 which means around 39 actual.

 

short trips

Xvs' short trips in the city are what's killing his mileage. From http://priuschat.com/forums/gen-iii...power-mode-in-city-mpg-stats.html#post1119831

Xvs, did you ever get around to answering the questions that I requested at http://priuschat.com/forums/gen-iii-2010-prius-fuel-economy/80123-eco-mode-vs-power-mode-in-city-mpg-stats.html#post1122309?

 

NO!

If you want your mileage analyzed get the Auto Enginuity or equivalent and record the following:

• coolant temperature
• velocity
• MAF (Mass Air Flow) sensor (prefer gm/s but can handle lbs)
• absolute pressure

You'll spend about $250 on the Auto Enginuity unit and provide your own Windows or equivalent laptop. However, there are other systems that should be able to provide the same data points.

I'm no longer interested in trying to diagnose verbal essays of posters who fail to bring empirical data to this forum. Auto Enginuity is not the only source but without those four data elements, it is impossible to say what is actually going on.

Bob Wilson

 

Unfortunately, we have some folks here who aren't even willing to fill out my questionnaire and followup on some issues when directed, most of which are free.

As you've seen, some of them bellyache, complain, claim they're "struggling", yet give no details as to their struggle. Some of those are never heard from again and some return later, having sold their Prius or to ask us about selling it.

Those whiners that do sell/trade in end up replacing the Prius w/something that gets even worse mileage...

 

I quite agree!

If you want my advice, a reasonable price is $250 for an Auto Enginuity to get a set of data or equivalent.

I've had it with . . . (sometimes I have to vent) . . . if you really want to protect your $25,000 vehicle investment and get accurate data, meet us half-way. Get the engineering data from your Prius and share it with us.

I have infinite patience with those who make an honest effort to provide the engineering data we need. We can repeat the "lessons learned" but we've found in the past mixed results. Some choose not to take the advice and that is maddening. Others take it, echo it, and still choose not to use our "lessons learned." But if you'll gather the engineering data from your own data, we can explain what is happening in detail:

Notice it take 240 seconds, 4 minutes, before my mileage exceeds 35 MPG.

Bob Wilson

 

I have some ancient IBM thinkpad I might be able to use, although I'm not sure if the battery will last long enough to do the job. What I use now is a macbook air.

Any devices which will do the job for less $$ and/or have mac software?

 

Personally, before spending $250+, I'd start w/answering the questions as I requested and following up on anything we ask you to check on. I'd also at least partly block your grille until get gets too hot out.

Again, if you're doing only 2-3 mile short drives in San Francisco (presumably in bad traffic, w/lots of stops and starts and hills - but we don't know), don't expect to get much better than the 36 mpg, you're reporting. Short drives are killing your mileage. Stopping and starting is very wasteful too.

If the roads and traffic conditions are conducive to it, I'd use pulse and glide. Search for those keywords in the Gen III forums.

I don't know if this is a great thread on it, but http://priuschat.com/forums/gen-iii...pulse-glide-warp-stealth-help.html#post922878 has suggested zones on the HSI. Unfortunately, my skim of http://www.cleanmpg.com/forums/showthread.php?t=25579 doesn't reveal too many details on 3rd gen Prius specific P & G.

 

There are some others coming along, Scangauge and Ken's box, but I haven't tested them. I use my wife's MacBook with an Intel CPU with a windows emulator to run Auto Enginuity. However, I've read about but not yet tested:

pyOBD - Open-source OBD-II diagnostics

It looks to be more reasonably priced and should work on a Mac. However, I've not bought one, yet, to test.

But we can post the "lessons learned" (the questionnaire) and (almost in unison):

• tires - run at maximum sidewall but check them for abnormal wear. Badly aligned tires increase rolling resistance and impact handling.
• speed - slower is better, find slower traffic to follow or a route less traveled that avoids a lot of stop and go. In commuting, experiment with different routes and consider using a different but more efficient route going in different directions.
• hills - go up as slowly as safe, following slower traffic if possible. Avoid accelerating up a hill as much as possible.
• warm-up - consider a block heater and keeping power loads low for first few minutes

Now if you are still concerned about your Prius, find a circular route that you can drive on cruise control at a set speed, say 60-65 mph.

Drive your Prius to the route and do one loop to make sure road construction and traffic will let you drive on cruise control at a given speed. At the start of the second loop, reset one of the trip meters and record the values when you complete the first loop. Compare your indicated mileage to this chart:

If there is a significant difference, there may be a vehicle problem because a relatively flat, circular route, 10 miles or longer, will eliminate the major causes of low performance.

Bob Wilson

 

Okay:

What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)

36mpg using Eco mode, less using other modes

What fuel economy are you expecting and why?

Over 40mpg because others report this

What are the approximate outside air temps?

50-65 degrees F

How long are your trips?

Usually 2-6 miles

How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here)

Battery and car are less than a year old. I can't test it until I know the procedure for a 2010 Prius II.

Have you had your alignment checked? Any pulling or abnormal tire wear?

No, no, and no

- How much of it is city vs. highway? Roughly what's the average speed in overall and and of each segment? Is there a lot of stop and go driving?

Almost all city. Average speed is about 15-20mph, stop and go has to do with traffic lights and stop signs. I try to avoid using the brakes as much as possible and always have. For instance, there's one street I drive down which has traffic lights timed for 15 mph, but no one knows it. So I go 15 mph, which causes some cars to angrily pass me, rush to the red light, and then have me beep at them as I glide up when it's turning green.


- What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.)

A mixture of flat and hilly. I don't live in a hilly neighborhood.

- What are your tire pressures?

Standard pressures 35/33 Yokohama Avid

- Is your oil overfilled? (i.e. above the full mark on the dipstick)

I didn't check but it was done by the dealer. Would this hurt mileage?

- Make, model, year, engine and transmission of previous car? (e.g. 08 Honda Civic Si 2.0L 4 cylinder, manual transmission) What did you actually get on the same trips/commute? (Please give us actual numbers, not EPA ratings.)

1992 Saab 9000 CD. 4 cyl automatic weighing 4300 lbs. I got 12.5 MPG.

- What region/state are you in? (if you haven't set your location)

SF, CA

- How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?

Trying to drive slowly and carefully, gradual acceleration, gradual braking.


- What modes are you using, if any? "normal", EV, power, eco?

Power was getting me 27mpg, normal 31, eco 36.

- Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on?

I open the garage door, back the car out, get out of the car, close the door, wait for traffic to let me back out, and go. This takes about 2-3 min and by this time the ICE has shut off.

- Are you driving using D or B mode?

D

- HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to?

Usually off.

- Are you using the factory tires and wheels? If not, please indicate tire make, model and size (e.g. Goodyear Assurance Fuel Max 185/65R15).

Yokohama Avid that came with it


---

By the way, I just changed to the engine graphic display to see what's going on, and I notice that when I accelerate enough to turn on the ICE, then coast (glide), the ICE stays on for quite a while, even at speeds of 30 mph or so, and even when the battery is more than half full. I don't know if this is unusual.

 

The advantage of having a recording OBD device is you can analyze your own data. This means you'll be able to see patterns and tune your own driving. There is no guarantee but having the data makes it possible.

Good luck!

Bob Wilson

 

It's the gliding all the time that's doing it. Slow starts, gliding... your Prius is constantly trying to recharge that depleted battery. Instead of slow starts from a standstill, give it a bit of gas (think snappy acceleration), and then glide down to the next stop, rather than trying to keep it in battery mode the whole time.

Not only might this improve MPG, it will keep people from honking at you angrily. Give it a try, what do you have to lose?

 

tips

Thanks!

Concur w/the hints given so far by bwilson4web and Rae Vynn. Definitely bump up the tire pressure and grille block w/current temps you have.

It's not a good idea to always accelerate so lightly that you're trying to keep the ICE off. As mentioned in the 2nd gen 5 stages PDF:

I've had a dealer overfill my oil in an oil change before and it's happened to countless others here on PC.

Regarding your morning routine, although Beating the EPA - The Why’s and How to Hypermile - CleanMPG Forums is probably WAY overboard, I think the back into garage (face-out) routine is a good idea. I don't know if your garage makes it easy to back in. But, if it's safe and easy, back in instead.

That way, when you pull out (forward), you're ready to go, and yes, shutdown until ready to pull out. Xcel's (Wayne Gerdes') logic is right here. Your fuel consumption is way high w/a cold engine. When you return from work/reached destination, your ICE's warmer and thus consuming less fuel or you're in EV (or can force it) for the back in. Same goes if possible at work. (I don't even do this as backing in can be a pain, but at empty parking lots, I do try to find spots so that I can pull forward to leave.)

Those 2-3 mins in the morning w/the ICE idling is time you're getting 0 mpg.

You can check your 12 V battery w/a cheap volt-ohm/multimeter you can buy from Radio Shack. But, unless if you've drained it completely by leaving a light on or something, it should be ok, for now.

BTW, it's VERY unlikely your Saab 9000 weighed 4300 lbs. That's current medium sized SUV class and far beyond most medium sized cars (Camry, Altima, Accord, Malibu, etc.) 1990-1998 Saab 9000: Technical Specifications - Consumer Guide Automotive claims a max of 3260 lbs. You're probably confusing gross vehicle weight rating (GVWR) w/curb weight. Cars have become very bloated in terms of size and weight since 1992.

BTW, I looked up your Saab and per Side-by-Side Comparison, the EPA numbers (after adjustment by formula) were:
15/23, 18 combined (for non-turbo)
15/22, 18 combined (for turbo version)

Since your 12.5 mpg is well under EPA city numbers, it's not surprising that you're well under as well on your Prius.

Don't expect miracles due to your short trips and all the stop and go.

 

Hi Bob,
I want to log my Prius. Is it necessary to buy "Toyota OE coverage option" with the scan tool to produce the logs you have shown us? Thanks.

Olivier​