Two Prii, different mileages

[pilot_dude]

I have two Prii, one a 2005 model and one a 2006. Over about 6 months I've compared the mileage and found that under the same driving condtions, same driver, etc. I get about 4-5 MPG better mileage out of the 2005.

Specifically, in good summer driving condtions, driving as conservatively as I can, I can push the mileage over a tank up to 51 on the 2005, but I can't get better than 46.5 on the 2006.

In winter both go down as expected, to around 45 out of the 2005 and 41.5 on the 2006.

That's ~10% difference between the cars, which seems significant. I bought the Prius in part for the good mileage, and I know not to expect as good as is on the sticker. But this difference really bothers me.

I checked the tire pressure. I've talked to the dealer about this, and they've done a diagnostic which turned up nothing. I'm not confident they're going to be too helpful.

My questions are:
- Can anyone else confirm different mileages on two Prii under the same condtions?
- Is it reasonable to push for some action on this from the dealer?
- Do I have any legal basis? If so how to proceed?
- What kinds of things could cause this difference?

[Paul R. Haller]

I have the exact same scenario on my 05 and my 06. I chalk it all up to that the 06 is not yet fully broken in. The 05 has almost 20,000 on the clock and the 06 purchased in August this year has just over 5000 miles. In 15,000 more miles the 06 should do the same as the 05. But ,after being in the car business for 30 years, it is not uncommon for 2 exact cars to vary by as much as 15% in what they achieve in milage with all conditions as close as possible. They are not a single die cast piece. They all are a collection of pieces and they all are a little different. hense, a variation from car to car.

Before getting excited (legal action?!?) give it a year. My guess is that you will see them both giving you nearly the same mileage after the 06 is broken in.
-Paul R. Haller-

[Tideland Prius]

so you want to sue the dealer or Toyota because of this?? How typical.

First off, what's the mileage on both cars? By mileage, I mean how many miles on them? Chances are, your 05 will have a year's extra right?

That's extra year is enough to further break-in the vehicle. If you want an apples-to-apples comparison, it would be two Prius of the same year bought within days of each other and driven at same no. of miles.

IOW, your 05 has broken-in the engine and tyres moreso than your 06.

Ah, but you say "doesn't the manual state the break-in period is the first 1000 miles?"

Yes it does but it's not like the engine suddenly stops smoothing itself out at 1000 miles. How do I know? Well, even this past summer, I was getting better mileage than my first summer (2005) and this past summer was hotter which meant more A/C use.

So, if I were you, I would keep track of the 05 mileage right now and come back next year and check that with the 06 and see if it's similar

[berylrb]

Hey welcome to Prius Chat pilot_dude!

Please share some specifics: mileage, tire pressure and tank fill up method for starters.

And hey, hang in there!

[Charles Suitt]

Now... THAT'S FUNNY..!!

Considering sueing the Dealer over MPGs? Read the window placard on which the EPA estimated MPGs are listed. There's a paragraph assuring you that your mileage WILL vary.

I must confess that a Plantiff does not need a CASE when filing a lawsuit, just a LAWYER. But then, frivolous lawsuits are thrown out by Judges much of the time.



Thanks for the laugh.

[IsrAmeriPrius]

Do both cars have the same primary driver? The Prius computers remember the driving style of the driver(s) and adapt the hybrid synergy drive system to get the best performance accordingly.

[tomdeimos]

You might want to swap tires between the cars. Worn tires will get better mpg, and also have smaller size so mpg will look even more inflated.

[flying]

I have exactly the same circumstances as you do! No matter what we try, the 2006 always gets at least 4mpg less than the 2005. Believe it or not, I have two friends w/ 2006s who are also getting the identical differences between the 05 and 06s. One thing that I have noticed w/ my 2006, is that the compressor for the a/c runs MUCH more often than the 2005 w/ same outside temps and same inside settings. I dont know if this is the reason for the difference or not. No matter, I still wouldnt want any other car. :P :P

[narf]

Like everyone else said, a 10 percent difference is certainly within the realm of possibility between individual cars. Are you quoting MPG that you calculate, or what is displayed in the consumption display? The displays can vary by around 5% between cars easily (My 05 always read about 7% high, my 07 seems spot-on so far.) If I just went by the display on both cars I'd be pretty disappointed with the mileage in the 07, but comparing the calculated results of both cars the 07 is getting better mileage for its first 1000 miles than the 05 did when it was new.

I tracked the mileage of my 05 for 35,000 miles, and the mileage continued to get better until the day I sold it. Some of that was caused by the tire wear which causes you to overestimate the distance you travel as the tires get smaller. Other causes include the reduced friction of components as they break in and wear together.

If you have long term calculated data on both cars, how does the mileage on the 05 compare with that of the 06 when they are the same age?

[tochatihu]

Possible, but probably rare: One vehicle has set its rear brake shoes to drag a little bit. Prius with rear drum brakes use conventional self-adjusters that set themselves during braking in reverse. No guarantee that they will always reset themselves perfectly.

It is pretty easy to lift a rear wheel, makes sure it spins nice, and back off the shoes if it does not (there is a little access hole to allow you to turn the whatchamacallit). A recommended procedure prior to any high-mpg driving event.

Disclaimer: system is as described for the classic Prius. May be slightly different in the new model?

Or, maybe your parking/emergency brake pedal is clicked down one notch and you haven't noticed the warning light?