Newly 2010 Prius Owner 40MPG

Dr. Prius is estimating hybrid battery (big battery) health.

My Prius I only get 40 mpg. 200k and the original battery. I think I am in the same boat.

 

Winter and city driving are not best friends to MPG.
Wait a little for warmer weather and do an out of city trip. Your MPG should be better.

 

I would begin with the easy and obvious things. Properly inflated tires, per the label in the driver's door jamb. Clean air filter. Offload excess weight. Then get out of the city and take it for a decent 55-60 MPH drive. As previously mentioned, fuel efficiency suffers in cold weather, and with winter-formulated gasoline. I would think that the effects in Houston would be less severe than here in New England, but still measurable. All other things begin equal, lighter wheels, and lighter tires with low rolling resistance will provide the greatest fuel efficiency in stop-and-go city driving. On the highway, at mostly constant speed, the detrimental effect of heavier wheels and tires is negligible.

My primary car is a 2021 Prius Prime. Like you, though, I just purchased a well-used (and in my case, mostly dealer-maintained for 130,000 miles) 2010 Prius IV. This will be my youngest daughter's first car, and the one in which she will learn to drive. It is now my daily driver, so that I can find and fix any problems (like needing new shocks!) before she begins driving it. I have done most of my own car maintenance and repairs for the past 40 years, but no longer have an interest in anything but the simplest DIY work. If you haven't already done so, I would take it straight to the Toyota dealer and let one of their experienced technicians change the oil and have a look around the car. They see the same things, over and over, and will notice things that you, as a new and inexperienced owner, will not recognize. They will use the best and latest diagnostic tools to identify problems. It's a bargain, even if you only do it once.

 

Welcome! And congrats.
Contrary to a previous comment, city driving really is a hybrid's friend if you drive it intelligently. In my wife's 2017 I get about 60+ mpg in the city and about 52 on the interstate. And Houston only has winter for a few days every 30-40 years, so that's not a factor.

Checking the 12V is a good idea. Replacing it if it's bad is a good idea. But check it first. Remember that the first step in a screwup is always an assumption.

It's very likely that your reduced traction battery capacity is partly to blame for the disappointing gas mileage. But as slowmachine said, check the tire pressure and other things that can cause drag.

One major detriment to fuel economy in any car powered by internal combustion is short trips. Also, if you didn't know it already (apparently few drivers do know it), the biggest fuel waster is late, hard braking. When you do that you take kinetic energy that could have gone back into your battery as regenerated electricity to move you down the road again and you convert that energy to heat and brake dust. It just clobbers your mpg. This guide is for the 2nd generation Prius, but it applies well to your 3rd generation. I learned a bunch reading John's stuff. http://john1701a.com/prius/documents/Prius_User-Guide_iconic.pdf

 

It never hurts to verify the accuracy of the Guess-O-Meter (GOM) with hand-calculated MPG numbers for a few fill-ups. I’d be focusing on the 12V battery, as low voltage can cause problems with many systems in any modern car. Until then, just fill it up when you get down to 1/4 tank.

 

Any fuel guage is just an estimate of remaining fuel. It will all depend on how you drive.
And what condition your engine is in. Time of year... several things.

 

That's true overall but short trips in winter are mileage killers because MPG is poor until the engine warms up.

37% on Dr Prius is very low. Is it the original battery? It could be good for you to post a screen shot of the battery monitor page for us to comment on.

I recently traded my 2010 Prius with 105,000 miles, was getting in the low 40's.

 

Start here, for common new-to-Prius issues:
Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat
Unfortunately it doesn't cover old-car issues, such as excessive brake drag.

See also:
Why mileage gets worse in winter | PriusChat

 

I'm not an expert on this but it looks like it's hanging in there.

BTW, I meant my MPG was in the low 40's. With Dr. Prius my battery was in the 50s.

 

Yup. That's pretty much what I said, but also said Houston doesn't have much in the way of "winter." Still, short trips are a killer. Example: most of my wife's driving is 10 miles or shorter. She averages about 52 mpg. Last week she went to a place about 20 miles away and stayed off of the death trap we call US 19. She got 70 mpg.

 

You need a tuneup, new spark plugs. And replace all fluids specially transmission. Both engine and inverter coolant. And also engine oil. Also reset your computer as well by disconnecting the battery overnight. Guarantee you'll be back to 50 mpg.

 

@PriusCamper got my into looking at voltage diff. when analyzing Dr. Prius screenshots.

At 0.20V your battery is certainly starting to get old. It probably spikes past 0.40V while driving so it may be time to consider replacing or balancing the battery.

 

After my service in the past summer, which are new 12V battery, OCC install, intake cleaning, new ICE coolant, rear rotor & pads replacement (this made huge effect because previous pads were dragging). My 2010 @256k didn't go below 43mpg during the cold IN winter. And yesterday, after the gas fill-up, it showed 60+ mpg to drive back home for an 11-mile trip. Surely it was already warmed-up until gas station in nice weather.
ECO mode doesnt matter, use it in normal mode in the city. And maintain that car very carefully, because it's (2010 and 2011 years) very prone to have serious problems if you dont care. And the story starts with irregular oil changes. Never ever exceed more than 5k. I only use Penzzoil Ultra Synthetic and Mobil 1 Extended. Thanks to this forum, I learned everything from scratch

 

Doesn't help much, if at all, and in my esperience makes it harder to modulate, way too much pedal travel.

That could be a significant factor. Start window-shopping hybrid batteries. Being in the States, there's $1600 with free shipping option that's very interesting: new prius batteries. They're available for second and third gen. From what I've read the install manual is mostly written for second gen, a little fuzzy regarding third gen.

 

ECO mode primarily makes the throttle feel more sluggish to encourage you to accelerate more slowly. If you accelerate equally, ECO mode won't help - it'll just make you push the pedal farther for the same acceleration.

But ECO mode also makes the AC a little less effective, which improvement mpg slightly if you are using the A/C.

 

The mileage going down double seems to be normal. Mine will say any where from 540 to 580 for a tank and I get about 410 to 450. Last tank I got 44 MPG calculated although the dash said i averaged 46 to 47 usually. Filled up this morning and it said 541. Drove 30 miles to work and my new distance to empty was 488.