Extremely low MPG, could the battery be going out?

I'm not sure how long you've owned the car or if your mpg's has suddenly lowered from a higher number or if this is what you've been getting all along. If your in northern Ca. and the temps. have suddenly gotten a lot colder that is one reason. Do the usual checks. Clean air filter, oil fresh at the proper level and the proper weight, tires up to proper pressure (42psi front, 40 rear is what I use). These places are a good starting point. Also if tires are non low rolling resistance that will knock your mpg's a little as well as front end being out of alignment.

 

On gasoline engines, the air filter is generally irrelevant to MPG unless it is so clogged that the engine is choking.

Clean air filters are nice for other reasons, but are not an MPG fix.

 

For starters, check everything in this questionnaire:
Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat

Also, check for brake drag. This will be detectable as too-warm brakes.

 

No the air filter alone won't do it but it could be a combination of a lot of other things like low tire pressure, heavier oil, front end out of alignment. If the basics are all ok then you can worry about more expensive things. A low or dying 12v. battery can trick the gas engine into running more than it should. A bad hybrid battery is the most expensive problem. Keep an eye on the hybrid battery indicator. It's normal for it to go up and down more so if your in hilly terrain or stop and go traffic but it should go up and down smoothly. Erratic or very quick up and down movements is a cause for concern.

 

Daily commute = 3 miles of highway and 3 miles of city streets. How long does it take for those 6 miles? The first 5 minutes of my 23 mile commute are typically 23-28mpg as the car warms up and does it's thing. The second 5 minutes are ~ 55-75 mpg as I go through a handful of miles in 40-45 zones. After that, mileage sits around 43-48 depending on highway speeds.

Do Gen 3's do something similar?

If you only have a short commute, you may not see much of the improvement that comes after the first five minutes.

 

If you're seeing abnormally dropping battery state, there's a pretty cut-and-dry hybrid battery check the dealership can do, for about $100 I think. It's often referred to as:

Hybrid Health Check

Google that expression for more info. Currently Toyota's offering this through dealerships in Britain and Ireland. And I believe it's readilly available tool in their diagnostic software (TechStream) world 'round?

Still, firstly: I would check the "low-hanging fruit" issues.

 

Welcome to Prius Chat .

Where in the great state of California are you located? The commute you have is very short and the warmup cycle may just complete prior to you reaching your destination.

Are you the DIY type?

If the car has had short trips in the past you might have some carbonized build up starting in the egr circuit affecting performance.

Check out the Gen3 maintenance section for a pinned thread by @NutzAboutBolts and you’ll see several videos . The one I would focus on is the egr pipe cleaning as that will give you an indication of what else might be lurking.

Keep us posted .

 

You should take a long drive like 50 miles to see if your fuel economy improves. By doing this allows the car to warm up properly.

 

Your trips with 55 mpg one way and 34 mpg on the return trip seem typical. That averages to 44.5 mpg, which is very close to the fuelly average for the '10 model (45.3 mpg).

As Bay Stater wrote, take your Prius on a long highway trip (preferably when there is no traffic )and make sure to set at 70 mph or less. The cruise control helps to neutralize driving habits. Don't try this during rush hour. Look to drive 60+ miles and make sure you measure round trip. Your mpg should be in the 50's.

 

Make that 42.0 mpg round trip.

(Do remember that for round trips, one cannot do simple arithmetic averages for MPG, because the denominators (gallons) don't match. Simple averaging does work for metric style liters/100-km, or the English equivalent in gallons/100 miles.)

 

how are the tyres pressure?

i think the hybrid battery is fine.

 

It's your commute distance and time. When the engine first starts, it's cold and inefficient. Also, the battery is helping it out in a big way. Once it warms up after about 5 minutes or so, it has to repay the loan; in other words, put that electricity back into the battery. By the time the engine has finished recharging the battery and you're finally ready to take full advantage of the hybrid system, you're at work. Ten minutes is where it just starts to get really good. I don't know if the regular gen 3 shows one minute gas economy bars on the touch screen like the PiP, but it's very telling on mine. Looks like a side view of a steep stairway.

 

The regular Gen3 does have this display screen, though most of us spend most of our driving time with the HSI screen up instead.

OP should certainly try this display a few times.

 

Not the HSI. This screen.

 

It may not be relevant to the OP, but weight plays a large factor. I had my lowest mpg on my last tank, which was 46.8. The difference was that I took a road trip with 500 lbs in luggage and passengers. Driving alone, I would have averaged 53 mpg on the same tank.