07 Prius really bad mpg

Have you seen this post already?

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

 

Don't waste your money with the battery test, your bad mpg is due to your 5 minute drive. The prius only gets efficient after it completes it's warm up stages. You are already at your destination by the time that happens.

Also the use of the heater/ac will reduce the mpg too

 

What JC said.

Also, unless you live at the bottom of a big hill, I wouldn't expect the battery to be in the green when you get home. Probably in the upper blue area. I gather that you're in a lot of stop and go traffic. That will drive up the battery charge and, with your short trips, you never get the chance to use it up.

Short trips are the bane of fuel economy for any car. The advice I hear most often is to combine your trips. But at only 4,000 miles a year, perhaps you don't have very many trips to combine.

 

If you are not already doing so, you might get a little help by allowing the gas engine to cycle through one time before you drive away. It automatically comes on a few seconds after you power it up. The car is much more efficient after that engine turns off at the start of your drive.

Now that you're into the colder seasons the car's mileage tends to drop anyway. Gas engine warm-up times increase. Also, using the defroster and heater will cause the gas engine to fire up more often.

The main culprit, as expressed above, is the short time of your drives. The car is designed to be driven and it's not even getting time to warm up before you're turning it off again. During times of the year when I have to use my car like yours I will drop from the normal 43 mpg to 34 mpg in decent weather with no a/c, heater or defroster use.

 

Winter tires can be an mpg killer, check the pressures

How are you calculating mpgs

A block heater might help, try to do as many errands in one trip as possible

Drive to the furthest, and work your way home

Prius kings is a chain, be careful, and don’t let them talk you into anything

 

AND.....you can't really trust the onboard computed MPG numbers.
Reset the ODO and divide miles driven by gallons put in the tank.......over several fills.

But it sounds like you have enough different indications that you know the mileage isn't really that good.

Alas, with a 5 minute trip to work and back it might not get any better.

Have you considered a bicycle ? City bus ?
Plug-in hybrid ??

 

Don't forget partial blocking of the radiator during the winter months.

 

4,000 miles per year is more than 10 miles per day.

The surprising thing is that you were getting 45 mpg when you first bought it.

 

Some things not yet mentioned that can bring down mpgs on an older car:

12 v

Hybrid battery

Fuel injectors

Plugs and coils

Oil burning

Air and cabin filters

Throttle body and maf

 

As there is no mention of any warning lights, we can presume there is nothing the ECM can "see" that is causing the higher than expected fuel consumption. This suggests that the AFR (air fuel ratio) is correct and that the engine is operating normally, be aware that it is more than possible to have a bad sparkplug or coil and no fault codes or warning lights; either of those will drive up fuel burn.

As we have started seeing colder weather, it is important to remember two important things about a Prius:
1) If you make high heating demands, the engine RUNS to warm up the coolant
2) If the coolant is too cold, the aux heater is activated to make up the difference

If BOTH are happening, that burns a TON of fuel because the engine is running to warm up the coolant AND providing HV power to the grid (aux) heater circuits. Why would this be? Well it seems like the coolant is either not staying warm (thermos system is malfunctioning) or the thermostat is, causing colder than normal engine operation; which BTW will, all by itself, increases fuel burn.

 

has anyone mentioned the bladder in the gas tank dosent expand as easily in cold weather so you are getting less fuel in the car when you fill it up..

 

No. Based on what? Even if so, the OP clearly understands that MPG = Miles driven / gallons burned as they stated that only 7 gallons was used to go ~ 200 miles.

 

If I had to drive 5 minutes twice daily, which I've done when I live couple miles from work, MPG will suffer, but you should be able to boost to 37-40 MPG.

For these 5 minute short trips, when outside temps are below 50F,
- 100% grill blocking. I use Coroplast free from the local carpet store. (They are the backing to carpet sample foldouts and are discarded often) This helps for warm up, and also for maintaining ICE temps when engine may be running but not under much load.
- Keep heater off
- watch instant MPG indicator, to keep above 50 as much as possible.
- no warm up,
- get to speed and let off accelerator just enough to maintain speed.

Pull grill blocking for longer trips, unless you can monitor ICE coolant temp.
ps. I've been using grill blocking during winters in Utah for 9 years now. I get 50mpg in summers, and drop to 44mpg as outside temps reach 32F (without grill blocking). With blocking, my mpg returns to 50mpg even in cold winter days. Started this with my 2004 Prius blocking all but the bottom, and my 2010 Prius blocking 100% of bottom grill. I keep designing 12v auto Louvers in my head, but have yet to make one. I should say your winter mpg with blocking won't improve more than what you normally get in summer mpg without it. How you drive will get you to 50mpg ?can? be easy, even 60mpg is possible but harder.

 

great tips, thank you!

 

what did prius kings have to say?

 

Whats this mean?

 

There are countless threads about it here. This is one:
grill blocking | PriusChat

Not something you'll be having any need for unless maybe you're going to Tahoe in the winder.