Consistently low mpg - Battery issue?

unlikely. we need more info, but a low battery gauge has never been a sign of a bad battery. in fact, i don't recall ever reading about anyone with a consistent 4 bars.

did he take it back to the dealer after seeing these mpg's on the first tank?

maybe the 12v is low, have you tested it?

how many miles on her?

how many miles does he typically drive? short trips return low mpg's.

 

has he asked the dealer why the bars don't go over 4?

 

6 is average, but there are certainly times from 2 to full.

 

does he do a lot of short trips?

 

Obviously I get 42+ MPG in probably 50/50 town and interstate driving. 80+% of my trips are in town (today maybe 8 miles doctor, bank, dump, grocery at mostly 25-45 MPH) but probably 70+% of the miles are 70 MPH with cruise often used. I use no tricks. I do use Eco on the throttle and Auto on the HVAC at 76 in summer and 68 in winter. Temps here vary from 100 to 20. I do watch my tire pressures and run 42/40.

I'd experience MPG higher than my overall average for city driving He should too unless there was something odd like lots of idling with the HVAC set to 70F, rocketing off the stop sign, carrying 1/2 ton of stuff constantly, using a roof rack, big wheels, wide tires, etc.

My battery probably indicates 3 to 8 depending on what I'm doing but it certainly is more than 4 90% of the time.

I'd escalate to the Toyota customer representative at the local dealer and then beyond if you don't get satisfaction. I'd ask that the traction battery be tested and individual cell readings be provided to you in writing.

Tell him to look at the manufactured date on the tires sidewalls as tires age as well as wear. It hurts to replace them with good tread, it can hurt even more to not replace em. Also check the engine air filter, some critter could have gotten in there.

 

After 2 years on the dealer's lot, the 12v battery is almost certainly not "good".

 

This is my car - my brother was very kind to start this thread and point me to the forum. It now has about about 3300 miles after 2 years of use (my wife and I live within walking distance of our workplaces, and the car is mostly used for errands). I wasn't too concerned about the low mpg in the first year - thought it was perhaps a break-in issue. I have taken the car to the dealer for scheduled maintenance every 6 months, and assumed they checked the electrical system each time.
Now that the mileage issue hasn't improved after 2 years, I must assume it it a traction battery issue. The car runs very well otherwise - but the gasoline engine is clearly engaged more than it should be in stop-and-go driving. I am very gentle on accelerations, gentle with brakes, run the car in Eco mode, keep the tires at 37-40 psi, and run the AC at 75 F. In Hawaii, ambient temperatures are always 60-90 F. It has been an excellent car, but the low gas mileage is definitely a concern.
After my latest fill-up, my wife took the car on an 80-mile all-highway trip to the other side of the island. The trip mileage when she returned was 48 mpg. But in 50-60 miles of city driving since then, the mileage for the tank has dropped back to 37 mpg.
The Servco Toyota dealerships in Hawaii are horrible for getting a car fixed. I usually have to schedule my routine maintenance at least 6 weeks in advance, and they would only offer me an earlier appointment to check the electrical system on a standby basis. I can't even get this issue looked at for 3 more weeks!

 

it's the short trips and lack of use. there's nothing wrong with your car, it just spends all it's time warming up.
i would learn how to test the 12v, or bring it to an auto parts store that can put a load on it and give you a readout you can post here. dealers don't understand them, and rarely load test them, if ever.

 

Ah, island driving. That gives some helpful background. So the car goes on lots of short shopping trips and gives what you think is horrid mileage? How short are those trips? I wonder if they are so short that the initial get the ICE up to thermal efficiency temp cycle isn't predominant in determining your MPG. I live in a community where my first mile is mostly downhill and supposed to be 25 MPH. Then I run a half mile on flat land and climb a hill accelerating to 55 MPH for the next mile. I watch the instantaneous MPG display go from 99 to the teens. I get 44 or so on the highway at 65-70 but to average 42 lifetime I must be getting in the high 30s for short trips where either the heater needs the ICE to warm up NOW to provide heat or the ICE is in run rich while warming up mode. I infer this from my estimate that more than 50% of my miles are at 60-73 MPH but probably 80% of my trips are local 10 mile trips. The longer my local trips the less those initial ICE warm ups would be affecting MPG.

The traction battery seems OK because of your highway MPG of 48 (you know the display reads 1-2 MPH higher than reality I'm sure). You must be switching to battery mode with ICE off successfully to get that unless she was on a trip with 55 MPH limits. When on that trip, did she happen to notice how many bars the traction battery displayed? Mine varies between 2 and 8 or so. I'm about to take a 40 mile mostly flat trip now and I'll try to notice more.

I think some trips with the MPG display set to instantaneous and noting the battery status bars might give us some clues on what is happening?

Sorry to hear of your poor service. Not the story here and so good we have 5 Toyotas in the family now. 2 v wagons.

 

i think 1,650 miles per year tells the whole story. i would be more concerned with the 12v health than the mpg's. heck, even the hybrid battery is a concern at those miles, once the warranty is up.

the good news is that a small gasser would probably return 15-20 mpg under those conditions. but the prius won't pay for the hybrid premium, although i suspect island gas prices to be quite high.

 

Should have bought a plug in hybrid or full electric!

 

All it needs is a new 12v battery and the installation of a proper battery tender. That 12v battery is toast.

 

or some butter and jam.

 

This morning a local trip. Then came home. Afternoon a 40 mile one way. Then back. This evening out 6 miles one way. Battery indicator didn't deviate from 6 bars or so (one from the top) even with temps of 93F out and HVAC set to 75F. Hard to tell how many from the drivers side or even from the passenger side with a seat belt on. Now the instantaneous readout was bouncing from 99 to 12 and back depending but the average was 44+.

You say the 12v was tested. How? If the traction battery is constantly trying to charge the 12v...

 

I live in Denver and have a 2010 Prius 2. A couple summers ago we spent a week in Honolulu. Stayed at a hotel on Waikiki beach and rented a Sonata. We did very little driving on the limited main freeway type highways in Honolulu. Driving in Honolulu was terrible with mostly stop and go driving just about 24 hours a day. I would consider you doing well to be able to maintain 4 bars in those conditions with the AC running. I would also say that getting 48 mpg on a drive from Honolulu to the North Shore and back was doing quite well as the drive includes climbing some pretty good sized hills.

 

I put my car into the diagnostic menu - it read 12.0 Volts in accessory mode, and 14.1 when the engine was running. I also took the car to the local O'Reilly store and had them run a check of the 12V battery. It tested good there.

 

I put the car into diagnostic mode - it showed 12.1 V in accessory mode, and 14.1 V with the engine running. I took it to the local O'Reilly and had them put their tester on it - it checked out good. I think my brother is probably right in suspecting some cells are bad in the traction battery.