40 mpg...

Winter and short trips take toll. My wife drives her 2010 3 miles to work and stops at daycare midway. Her mpg is ~ 40
When I drive I get ~50-55 mpg in her car but I take a much longer trips.
- Alex

 

The battery sounds low. I'm really not sure how those values are derived, suspect the first is equivalent to measuring voltage with the car off, with a multimeter. The latter should give at least 12.4 volt (that's what I'm getting on ours, so it's ok, lol). A 100% battery would for sure give over 12.6 volt.

Tire pressure is "good"? That likely means per the pressures recommended in the drivers door sticker. That pressure is a compromise, with one aim being to keep kushy ride. If you don't mind feeling the bumps a bit more, try running them up to around 40 psi, all around. Maybe a bit more on the fronts. Personally I set them all the same, makes life simpler at rotation time.

That mileage is troublingly low. Doubly so because the car bs's on displayed mpg, actual is likely more like 37~38 mpg, if you were to calculate. Just stick at it for a tank or two, see if it improves. Is this highway or city driving. What speeds?

All things considered, just stick at it for a tank or two. Try to adhere to speed limits, keep a good space in front, coast up to slowdowns. The less you need brakes the better.

 

fill out the 'why are my mpg's low?' sticky. that will give us more to go on.

 

How do you drive the vehicle? It's really hard to tell why you're getting low MPG without knowing more detail. Do you typically drive short trips? Are the trips mostly all freeway? Or city?

Take for instance I typically like to drive city routes since that's where I see my biggest MPG gains. If no one is on the road when I'm driving I will accelerate REAL gradual and purposefully drive under the speed limit and pulse and glide the entire time. All these little things add up over time and it just takes time to get used to driving habits. I think I would REALLY need to try hard in order to hit 40 MPG as I typically get 45 MPG when temperatures are in the single digits. Today's temperature reached around 40 today and I could already tell my MPG starting to climb. Can't wait to try and reach for the 60 MPG mark once it really starts to warm up

 

Ahh, Uber.

 

oh ho!

 

One thing I've really been trying to do lately is coast up to a red light. I mean I will start to slow down real early. Even if you've only gone down to 5 MPH, that's still better than a complete stop.

 

it's the last one in gen II prius fuel economy forum.

 

Welcome to the world of Prius:

Here you go:
Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat

Bob Wilson

 

you need a new 12 volt battery, that can cost you 5-10 mpg, see ned. you may want to research the tyres to make sure they are low rolling resistance. if not, that can cost 3-5 mpg, see ned. how fast are you driving on the highway? over 65 can seriously compromise mpg's. other than those, i don't see any problems.

 

Just to amplify the 12V issue:

• 11.9-12.85V - allowable, voltage without car charging circuit turned on.
• <11.9V - 12V battery has been run down and/or is failing
• 10.5V - 12V battery is toast, replace as soon as practical as starting becomes a 'crap shoot'
• 13.8-13.9V charging circuit voltage for 12V battery

What lights were burned out? The reason I ask is there may be a latent, switch defect that allows the bulbs to discharge the 12V battery. In particular, peek at the car after 3-5 minutes to make sure all of the interior lights are going out.

As the car run, it 'adjusts' the cold-start, fuel trim (i.e., mixture.) When the 12V gets too weak, this can default to an overly rich mixture. Also, the remote-access can not unlock the car.

Bob Wilson

 

1. One hp is ~745 Watts, which for a 12V battery which under charge is ~745 W / 13.8V ~= 54 A.
2. Cruising at 72mph, your expected MPG would be: These MPG values achieved by driving on cruise control on a 'flat' area and does not include acceleration or braking effects. One Prius trick is to learn how to follow slower traffic at a safe distance, say a moving van or delivery truck. The following traffic will see the truck and smoothly pass without 'setting their hair on fire' about the poor Prius stuck in traffic. Meanwhile, play some good tunes and enjoy the ride . . . like golf, the race is to avoid the gas pump. FYI, you have two trip meters, A and B. Use one for the tank and the other for 'test' segments to learn how the car really works.
3. Driver side visor light, make sure in the dark that when the car is off, there are no other lights draining the 12V battery. Day light it is harder to find these parasitic loads.
4. Used car warranties are negotiable. An Autozone or car parts store may be able to test the battery and provide an independent metric. WARNING: reversing the 12V battery polarity can destroy expen$ive controllers. You might want the seller's shop to handle the test.

GOOD LUCK!
Bob Wilson

 

I could be wrong, but I don't think the 12V battery is covered under warranty.
Take Ned's "52 mpg for this one" with a grain or two of salt.

 

If it really reads 11.5 with no load, it's dead by anybody's standards.
BUT......used car warranties often do NOT cover things like tires and batteries.
Regardless, you need a new one.

 

A few comments on the above:

1. If you change the display to show this:



it's easier to slip the car into electric-only, and keep it there. If you completely lift off the gas, then gently re-apply, while keeping it to the left of the center line on the bar (yellow highlight zone), the engine should stay off. Get too good at this, especially under moderate load, and you'll start to run the hybrid battery down excessively. Arrrow number 1 points to the hybrid battery state of charge indicator.

Running the hybrid battery down is not terrible, it'll just force the engine on, but use this trick moderately, you'll cut engine use without downside. I'd back off from this tactic if hybrid battery charge has dropped to around half.

2. I'd reserve B mode for LONG hills only. Like coming down ski hills. To slow on short down grades, just use the brakes as usual. B mode reduces battery charging, it's intent is to protect the battery from overcharging, coupled with protecting the brakes from overheating.

3. Is that a typo on the tire size?? Correct size should be 195/65R15? If they are 185/65R15, that might be a factor.