2007 Low MPG -- Can't figure out why

I haven't noticed any other issues but I haven't started digging into it yet. Being a compulsive researcher type, I look for where to start out here on the posts. As for what I have seen - my regular 80 mile round trip commute has a shallow hill that is not that long (best guess 1/4 mile long, no guess as to grade but not a really steep grade). MPG has dropped from 20ish on the uphill @55 mph to 10ish @ 55 mph and minimal battery assist; I didn't notice exactly when (most likely a 1.5 wks ago) since I don't pay attention until refuels. Rest of drive is relatively flat so I don't notice as much of a difference but looks to have slid 4 or 5 mpg, will know better when I cross check MPG at my next refuel. Coming up on a maintenance check time so I will have things gone over then and in the mean time check the same things in this post prior to servicing at the dealer. Will post if something changes.

 

^^^
http://priuschat.com/forums/freds-h...elevation-profile-route-between-2-points.html can take the guessing game about hills/grades.

 

I have a 2007 Prius touring and have been experiencing a drastic change in my MPG for the last year. after trying every thing I read on Prius chat with no luck,I checked my 12v Battery, low and behold the voltage was low. I replaced it myself with the new Yellow top optima battery and my mileage jumped back up into the high 40s around town---- it was running as low as 32 MPG

 

Scramjett: I read thru the first page and the last three pages of your thread. Based on my '07 HCH failing hybrid battery pack experience, I'd say your battery pack is past its 'best before' date.

I'd get a ScanGauge, set it up with some extra gauges (see x-gauges for dummies thread) that show:

• the battery SOC (shop manual states '60%' is its happy zone). You can drive and watch the Prius software 'sine wave' its way above and below the SOC 60% with a good battery; and
• cell SOC delta. It should read "0" %. If not, one (or more) cells is out of balance.

Out of balance cells seems to be an issue with the HCH II based on my experience (and chat room rants).


If your five year driving a Prius habits have not changed and the simple stuff has been checked, get a second opinion on your battery pack via the ScanGauge.


Good luck with your issue.


Cheers


Mike

 

Torque and PriiDash are better for analysis. Scangauge is better for instantaneous readout. Mangoose is a little iffy -- a Chinese clone and hacked software copy of Techstream Lite. It depends on how you feel about things like that.

 

This thread has read like a good novel as we drove our new/used 2007 Prius (pkg 4) with 22K miles (it lived on Nantucket) from Cape Cod to Indiana in the last two days. Since buying the car (from a Toyota dealership) last Monday, I have wondered if it was working optimally. Once I found the display screen I noticed it had gotten on avg 27mpg for it's previous 105 miles!! I was shocked and had immediate buyers remorse until I drove back to the dearlership 60 miles away and got nearly 50 on the way. They told me the car would need to cycle through 2 tanks of gas and "get used to me as the new driver" before I could honestly gauge it (all the while knowing I was about to take a trip across the country!)
When I got back to where I live, I got only low 30's around town and took it back again. I was taken for a ride (no pun intended) and told how to drive the car. Well, it seems this car runs optimally when driving 30-55 mph. Below 30mph, which is what I drive around my small town, yields pretty bad mpg. AND, on the highway for the last two days, we got 32-33-35-36 for the four tanks it took to get here (1,029 miles). Granted, we have a Yakima on top and we were driving into strong winds, and after we read the thread we checked the tires which were at 32psi, front and back.
I'm feeling like we need more time with this car, but I am strongly cautious and I am keeping meticulous track of what's happening. This thread was so inticing because we were also wondering why the engine doesn't use the battery more. The battery is constantly in the 7 bar green zone. Up hill it charges the battery and the arrow coming from the battery just occassionally blinks, which makes me think very little energy is used from it. Also, it has a really hard time picking up. I was leery to pass people because I couldn't gather speed quickly enough in the fast lane. Again, I wonder if this is a symptom of the luggage rack and wind, but still, it just seems low (and honestly a bit disappointing considering I could've bought a gas-powered engine that might have given me better mpg). That said, I was sad to see there wasn't a resolution. I will keep checking back in to see if there is one, and in the meantime I'm having a health check done here tomorrow morning at which I will be armed with a lot of knowledge, thanks to you all!
I do have one question for the originator of this thread: What do you get driving small trips under 30mph? Is that why you got the Nissan Leaf, because the Prius didn't live up to your expectations? Thanks

 

This is not expected. The only benign explanation I can think of from my experience is that the battery icon was slow to update.

The dealer statement that it takes two tanks to 'learn the driver' is BS.

Overall, your fuel economy is way below average. I suggest taking off the yakima and going for a round trip of about 20 miles at 60 mph after the engine is warmed up. Anything below 50 mpg suggests a problem. Important --, try the test on a day without wind. You have to remove as much as possible driver and enviro variables to concluded something reliable about the car.

The most common car problem with the symptoms you describe is an old 12v battery. If it is older than 2 or 3 years old, I suggest you replace it now and see how things are.

 

The Yakima will kill your mileage.

50 mpg is a little optimistic. You may need a couple tanks of gas for the car to break YOU in.

 

I didn't think the Techstream Lite was a hacked version. It was essentially an evaluation version unless you registered it (or found a bypass to make it appear as registered). You can also sign up for the 2 day $55 version and download the current version of TechStream Lite if you wanted to. The Mangoose cable works just fine for the few things I've used it for thus far.

I also have a separate TS compatible cable that can be used, but it only has drivers for Win XP (I'd have to find that driver disk again).

Jeff - If you meet up with Justin to try to trouble shoot, I could loan out one of the cables if you get TS. It might allow you to more easily monitor more information (I haven't used it yet for that, but I'd recommend a 2nd person in the car using the laptop).

 

As a neophyte to the Prius, I did a quick web search of PriiDash to see what that was all about and found this:

PriiDash(TM) - Enhanced Instrument Panel and Data Logger for the Prius and more

Awe inspiring to say the least, but not for the (like me) computer tech faint-of-heart (IMO).

One question with the sample (temp) gauges I see in the above link: what data is used to constitute the displayed "water temp overheat"?

Is it based on shop manual numbers?

Only reason I ask is this: icon of temp gauge seems to indicate 'overtemp' (i.e. red zone of gauge) at 195F (90.6C) yet shop manual 'thermostat calibration' seems to indicate thermostat not fully open until 93C (199.4F).

Thanks

Cheers

Mike

 

The 27 suggests many short drives without full warmup. That would be expected of both Nantucket and of car lot test drives.

Below 30 mph in my large metropolitan area, my 2010 can do fantastically well, 70+, when Spring arrives. (Translate that to 65 for a 2007). But as a new driver, you likely haven't yet learned how, and in a small town, it may not get sufficiently warmed up to achieve this. And the best mpg season has not yet arrived. But it will still crush a traditional non-hybrid, which also does terrible under the same conditions.

Strong headwinds and external racks hurt separately. Together, they are killers.

Please name one that would get better mpg with the top rack into the wind.

Since I learned to hypermile, my old Subaru gets above 30 mpg in standard conditions. But four days ago, with a fully loaded ski rack (probably smaller than your luggage rack) into a strong headwind, I couldn't hold it above 22 mpg. The same increase in fuel consumption would knock a 45 mpg Prius (the EPA highway rating of your car) down to 29 mpg.

In additional to your conditions and style, there could still be some factors with the car itself. For more help, please read and answer this: Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new

 

Found this interesting article 'predictive battery failure analysis':

Predictive battery failure analysis for the Prius Hybrid

In the authors opinion:

I think (please correct me if I'm wrong) that the x-gauge "cell SOC delta" could be the 'first quick check' to determine battery health.......

 

Agree w/all of the above. I find it impossible that any currently sold non-hyrbid, non-PHEV and non-EV would get better mileage w/a roof rack on top, in the same conditions, under-inflated tires or not..

Actually, that poster should answer http://priuschat.com/forums/gen-ii-...-answer-these-questions-esp-if-youre-new.html, which is almost the same. Otherwise, we're wasting time making guesses. First step is to get rid of the roof rack and box completely so that we have somewhat of baseline and 2nd is to properly inflate those tires. 32 psi all around is too low. For a non-Touring Prius, I'd go at least 38 psi front and 36 rear.

 

Oops. Fixed my link to the correct generation.