Fighting to barely get above 35mpg

Sounds like you need a 12 volt battery Megan...

 

I'd stay away from the Toyota OEM 12v battery as there are several aftermarket batteries that will provide longer life expectancy and they're not as overpriced as the Toyota oem. Toyota originally chose NOT to put a powerful 12v battery in the prius because there's very little energy required to simply boot up the ECU's. Once the car boots up the ICE starts via the main traction pack. There are several threads on PC where you'll find folks recommending the yellow top Optima battery. Optoma has had its ups and downs over the years but recently they've been getting pretty good reviews.
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I am just the opposite of Hill. I think the Toyota Battery is the best one right now. Has more amp/hrs. than the coveted yellow top battery. Also if you get the True Start Battery that Toyota is selling now, it comes with a very good warranty.

I bought one 18 months ago for the Gen II I had. Worked for me. I know of several here on Prius Chat that bought the yellow top recently and returned it and went with the Toyota True Start and have been pleased with them.

Do your research on the batteries. Buy the best battery you can that will fit your car properly. Remember, it a AGM type battery that has the special JIS posts on it.

Don't take it to the dealer. Get a new battery and DIY. The dealer charges BIG bucks for the labor to install it. You can expect to pay in the neighborhood of $150 to $200 for the correct battery for your Prius. They are NOT cheap like your Wal Mart batteries are...

How do you replace the 12v battery? | PriusChat

Ron

 

Whatever battery you decide to get, please be super careful about polarity if you need a jump start to get there, and likewise make sure whoever fits the battery is trustworthy not to reverse or short anything, not even for a split second. The amount of dollars damage from doing these things wrong is a lot higher on the Prius than with most cars.

 

Is that 40 mpg in miles per Imperial gallon or US gallon?

FWIW, 40 miles per US gallon is 48 miles per Imperial gallon. 35 miles per US gallon = 42 miles per Imperial gallon.

VW reliability ranges mostly from so-so to downright horrible here.

 

I was quoting 40 us mpgs, which is, as you said is 48 imperial. Any 2.0 TDI will do that without much trying. I think that the VWs over there were produced by your neighbours down south which may be some of the issue. We find them to be pretty good here. Alot more issues with modern BMWs, etc. That's my experience here in Ireland anyway

The new 1.6 TDI Bluemotion Passat is reported as doing 70 imperial mpgs on a few tests here, which is almost 59 us mpgs, not bad at all.

 

My wife was about to take our recently purchased Gen II on a long trip. I checked the car over, inflated the tires to 42/40, etc. Then I saw the thread on checking the 12V. It tested at 12.1-12.2V after sitting overnight, and dropped to 11.5-11.6 in Accessory mode. The car showed no symptoms, we were easily getting 48 MPG, but it made me nervous.

I checked out the Optima and Exide batteries online but wasn't sure they would arrive in time for me to DIY. So I called my independent mechanic, who said he had to charge me $200 for the OEM battery because he was forced to buy it from Toyota. But his labor - 22 bucks! I would have spent that on the metric wrenches/sockets. I considered it cheap insurance against a tow in the middle of nowhere.

 

IMO, you made a wise decision. Best of luck to you mkgrayfox.

Ron (dorunron)

 

[duplicate]

 

I've been getting 45-50 MPG in my first two weeks with a used Prius, with some variability. I have definitely been conscious of the fact that I have to "learn to drive a Prius," which requires a little more patience, and attention to certain techniques.

Also, I don't pay attention to that screen, it's bogus on a regular basis. My screen said 46 at the last fillup but I actually CALCULATED 49.3. So do yourself a favor and calculate actual mileage next time. Set your tripmeter to zero on a full tank, drive at least 250 miles, then filler up... calculate it yourself.

 

It doesn't hurt to ask the dealership for a battery replacement price. The price for install can vary widely, I've even experienced gratis for install, at another manufacturer's dealership, and the battery cost was quite reasonable. Plus, at least up here, there's a $12 refundable deposit if you DIY. I still went that route last time, but just saying.

 

Beware that your GenII has a fuel tank bladder. For many (but not all) owners, this adds considerably tank-to-tank refill variability. Because of this, its is better to compute average MPG over multiple consecutive tanks.

 

Yes, henceforth the bogus nature of the figures on the screen. My three tanks have been 53, 45, and 49. That's why I used the term "variability.

 

Hi Jason, if you're taking fill-up calculations then it's a really good idea to plot them on a spreadsheet or something. The tank to tank variability tends to give errors that oscillate from one fill to the next, so if you just take the trend line (ignoring those oscillations) then you get a really good picture of your true MPG.

BTW. The reason why these oscillations correspond with fill-up cycles is because any errors you make in the tank refill level, eg pump cutout point variations, result in an equal and opposite error component in the next re-fill. For example, if say you accidentally filled one gallon short one time then you would get an unusually high calculated MPG. However on the next fill cycle, since you are running a gallon short, you'll get lower miles and unusually low MPG.

There are of course other factors that give rise to variability, but these oscillatory errors due to tank re-fill variability are particularly noticeable if you graph it.

 

Yes, I know all of these things. There was really no need to bust out the technical thesaurus to describe human error to me. The point is to tell the OP that he should be calculating gas mileage himself instead of trusting a computer to do it for him. In the long run, this will give you more accurate figures.

 

Sorry for trying to help. A lot of people don't realize that one overly optimist tank usually gets followed up by an overly pessimistic one for the reasons I stated.

And BTW. Don't jump to conclusions about the accuracy of the reported MPG too soon. Mine was very inaccurate (pessimistic like yours only worse) when I first got my Prius (s/h in 2009). Over a period of several months the displayed MPG became more and more accurate, and now is very stable and accurate to about 2% or better (always slightly optimistic now btw). Apparently the ECU collects "historical data" that it uses to improve the displayed MPG accuracy.

 

I feel that in the Gen2, the computer is more accurate than going off a single tank fill. I track my tanks and what the MFD showed for the tank (I only reset it when I fill). The tank mileage can vary quite a bit with similar driving, but the MFD is much more consistent. However, as many others have noted, the MFD does seem to be a little optimistic.

 

This particular variability doesn't show up in the figures on the screen, but only in the numbers you calculate from the pump refill amounts.

This isn't about human error, but about mechanical inconsistencies inside the fuel tank bladder.

Yes -- in the long run. That means a running average computed over many consecutive tanks, not the calculated value for any single tank.