Decrease in gas mileage on 2010 prius

If your 12v battery is still original, I think you'll find, based on history of threads on PC, the 12v battery is the likely culprit.

 

you've done the battery testing, now you need to find out if those numbers meet spec or fall below. i am not qualified to answer. you can either search for threads with the answer, or wait until someone replies. whatever you do, don't take the dealers word, most are incapable of diagnosing a 12v battery. they will either replace a good one (and your mpg's won't change, $300. down the drain) or they will tell you it's fine, when it was the culprit all along. if you're lucky, they will guess right.

 

Probably includes any "diagnostics" done and labor charges.

SCH-I535

 

With 107,000 miles on our 2010 Prius we are still getting the same MPG's as when new. Weather
is the biggest influence on mpg's, more so than any other car I have owned. This is from driving
since I legally could back in 1966....

 

the oem is expensive and the aftermarkets are not much cheaper, although, they do pack more punch and can stand to be drained now and again which the oem does not appreciate. it's a small battery and not liquid, so kind of rare. dealers charge a fortune to replace so you can save a bit doing it yourself. i think the battery is $200. and maybe $150. for an optima yellowtop.

 

Another thing to look for is if the foot-operated parking brake is on (even partially) or if any of the brake calipers are stuck, imposing a drag. I would jack up the wheels and see if they rotate freely. The front, I suppose will move a few degrees but should do so freely I would presume (never checked the fronts on mine).

My MPGs initially were great and climbing into the early 60's and then they came down and settled around 55 in summer and 47 in winter (I have a 3.7 mile commute each way). Then mysteriously in the middle of last winter, they started to climb back up again into the late 50s and the car generally seemed to glide a lot better and easier and the pickup felt stronger. This improvement lasted for a week or so and then came back down. I suspected the calipers sticking and such and paid $50 for the dealer to do a brake inspection but according to them everything is good with the brakes and they aren't sticky. I always use the foot-park-brake whenever I park the car.

All parameters on my car are normal as yours and so I would be very interested in what you find out with yours.

 

See cwerdna's questionaire on fuel economy troubleshooting. It is a sticky thread. Could be alignment, a brake dragging (how does it glide now compared to before), or any number of things, but it is not normal to lose mpgs just by time or wear. I'm not sure what you mean about top end cleaning. And the treatment to clean throttle body sounds like something was dumped in rather than taking it apart and cleaning it, so I'm not ready to rule that out.

12V is a common issue, but yours seems ok.

 

i run mine at 40 f and 38 r, seems to be the consensus here for decent mileage, handling and ride comfort.

 

I'm running 51 psi in the Sumitomo T4s which were bought at the Toyota service center. Every two months, I top them off.

Bob Wilson

 

lawyers.

 

Nice soft ride!

 

2010 prius. I recently discovered that the passenger rear brake caliper slide pin was stuck. The frozen slide pin caused the inner rear brake pad to remain lightly applied at all times. I've owned the car for 2 years and 20K miles and gotten a consistent 44-47 MPG never knowing about this problem. From what I have read, these calipers can have this problem.

Only came to my attention once the pad wore out and started to scrape the brake rotor. Now the caliper replaced, car easily getting 55 MPG-65 MPG not trying that hard with low AC on. Could never get these numbers before. Friends wondered why my MPG was so low, now we know! Check all 8 brake pads for uneven wear or binding. I imagine that low MPG can only stem from two forces....forces that accelerate (engine, synergy drive, battery) but also drag forces (brakes, tires/rolling resistence, missing underbody panels, worn bearings, etc).

 

All cars in general goes through caliper pins seizures, its part of the maintenance list not problem list.

 

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I put fuel injector in as well as changed air filter .. mine increased . I wonder about gas filter changes!