Fuel Economy Survey- Am I Hopeless?

it's probably your 12v battery, have it checked, or just replace it if you can't determine how old it is. if it's the original, you're due for a new one at that age anyway. i think you can get 40 mpg in those conditions.

 

If you were only driving 1 - 2 miles, then I'd say that's about right. But 7 miles and 29 mpg? Long highway trip and 29 mpg? There is something wrong. You'd have to drive with one foot on the gas and the other on the brake, with all the windows down and all the accessories on....with a parachute to get that type of MPG's.

If you haven't already, you might want to schedule a visit to Luscious Garage and have them take a look. I would be concerned about this type of mileage. Sorry, not trying to scare you, but what you are seeing isn't acceptable and points to something with the car.

Luscious Garage | Hybrid Specialists

Lazy link added.

 

Try changing the 12v battery. Also, having heat on 78 keeps the engine running all the time on your short trips, and it does not have time to warm up. Blocking the upper grille should help the engine warm up little faster. Also, Try to have your tires at least at 38 psi.
Another possibility is that there is something wrong with brakes and they drag a little all the time. Mechanic can check.

- Alex

 

I think you should expect about 10mpg better than you are getting, tell the people at Luscious about your mileage, they will probably suggest a new 12v battery, good luck.

 

Thanks for answering the questionnaire!

Yeah, being in SF does NOT help w/mileage. Yeah, all the stops signs, traffic, hills and possible idling doesn't help, not to mention your short drives.

Before throwing money at a 12 volt, please run the test at Weird stuff happening? MPGs dropping? Test The Battery | PriusChat after the car has sat MANY hours or overnight. Please tell us the 3 values (not just 1). Don't go changing the battery first until you tell us the values...

If you have HIDs, you can avoid unnecessary cycles on the lights by toggling between off and parking light positions.

Weird stuff can start happening w/a low or bad 12 volt. Don't waste $ on having a dealer "test" the 12 volt (07 Prius Dead - Any Guesses? | PriusChat). If you're on you're original 12 volt, it's likely near or at end of life now.

Yep on all of the above.

Please see the better heater management tips at Why mileage gets worse in winter | PriusChat. I would NOT leave the heat in auto or at 76 all the time. I would ONLY turn the fan on (w/heat) either the engine's warm enough or when it must run anyway. If the engine's cold, then just turn the heat up and the fan off.

I personally block my upper grille in the winter (including now) even in the South Bay.

I think the OP can hope for 35-40 mpg or so given Most fuel-efficient cars and the details of their city test on the last page of http://www.consumersunion.org/Oct_CR_Fuel_Economy.pdf.

But, 29 mpg on a 600 mile roadtrip, assuming it was mostly highway is VERY bad and abnormal. When I've driven between San Jose and the LA area, where I'd do 72-78 mph and I've got the hills at the Grapenvine, I can still average over 40 mpg even though 2 of my tires aren't LRR.

 

Let the mileage accumulate for 5 or 6 tankfuls, it'll give a more accurate indication of overall mileage, takes a tank or two just to get out of the 40's some times.

Clean your cabin air filter
Check the ice filter, 40lbs of air in the tires, go to an auto parts store and have them put a gizmo in your obd2 port to read any codes, might turn up something interesting.
Yes get a new 12v and a battery charger, every two months charge the sucker(12v) just to top it off.

 

Changing the cabin air filter won't help w/mileage.

Yeah, the 12 volt may not be getting sufficiently charged w/such short drives. I ended up ordering an Optimate 4 (as I posted at battery tender/maintainer suggestions | PriusChat). It charges slowly enough that there's no danger of charging too quickly.

I've used black pipe insulation that I bought at Home Depot. I just stuff the the upper grille from the outside. There are many variations. If the pipe insulation is too large, one can zip tie it.

There are a bunch of old grille blocking threads here.

When I lived in WA state where it was much colder and stayed cold in winter, I blocked the upper and part of the lower grille. I had to zip tie the pipe insulation around the slats (better word for this?) of the lower grille.

As for turning the heat up and fan off, just turn the temp up, to say HI and then press OFF for the fan speed. You'll still get a bit of heat and more when you're moving due to ram air coming in. Again, once the ICE (internal combustion engine) is warm enough, it won't need to run to provide cabin heat. Unfortunately, the only well to tell how warm/cold it is is via a tool that plugs into your OBD2 port like a ScanGaugeII : Linear Logic - Home of the ScanGauge or Bluetooth OBD2 dongle and an appropriate app (if available) for a smartphone (e.g. Torque for Android).

 

Sarah, you're not hopeless. There's always something that can be done. Blocking the grill means buying some pipe insulation and sealing up the front grill from the outside. It is very cheap, very easy, and very reversible. Here's all you need to know: First Morning with a Blocked Grill | PriusChat

Soft tires have more drag than hard tires. You may want to go up to max sidewall pressure. That's the number stamped on the sidewall. It is probably either 44psi or 51 psi. There is no right or wrong number. It depends on how you like the car to perform.

Have you tried engaging then releasing the parking brake? It's free & worth a shot.

I do agree with the others. Something is wrong, we just have to help you find it and fix it.

Are the tires on the car Goodyear Integrity or something else? You mention that you bought the car used. How do you know the previous owner didn't swap out the tires?

Please go to Toyota Owners Official Website: Service Coupons, Owners Manuals, Service Scheduling and More to register the VIN. You can find the car's dealer service history. Let us know if you find anything other than oil changes.

 

Was this after the car sat MANY hours or overnight since last being in READY mode? If not, wait until tomorrow morning.

As for tires, you need to check their cold pressure, after the car hasn't been driven for many hours or overnight.

 

I'm no expert but from what I've read in these forums, the voltage amounts are low. It appears your 12V battery is suspect. Also, try keeping track of your mileage and gallons per fill-up. Are you really using 10+ gallons every 300 miles?

 

I'd say your 12 volt is borderline marginal, not terrible yet. There was one guy here who had trouble starting his Prius and found that via a volt-meter it was down to 3.1 volts! Now, that's BAD!

I've seen people here post voltage vs. state of charge charts here but the problem is, the car always has a parasitic load on the battery and putting it in ACC mode for even the 1st reading puts on even more load.

The SoC charts assume no load on the battery. And, from what I've found, the voltage test via the MFD reads a bit lower for me than putting a volt-meter on the battery terminals in the back (probably due to the ACC load). And, I have no idea exactly how much error is in the MFD's value.