very bad prius mileage

You are complaining about miles-per-tank, right, and not MPG? It sounds like the tank bladder in yours is crankier than average; given that, there's not much you can do about miles-per-tank.

 

I see you are relatively new here, but assume you have done some searching of the other threads from your original post. Winter mileage is disappointing for a lot of us. While some things help to mitigate that - what helps one may not help another. It seems each car can have its own personality a lot of times.

For me, in sub 25 degree temps - I get tanks that average high 30's and low 40's. Overall in these conditions I seem to average 42-43mpg unless I am really making an effort to use green driving techniques (aka pseudo-hypermiling). In the warmer months I can easily average 46-50mpg depending on how conscious I am of my driving technique. As the car continues to "break-in", I expect this may improve a bit; but I don't have unrealistic expectations.

FWIW, I have a partial grill block, engine block heater and maintain 44/42 psi in the tires. I also use a scangauge II because I like gadgets. This may not be want you wanted to hear, but hope it gives you some context for comparison.

 

For the winter, with no grlle blocked, or engine block heater, yes, 36 is normal. Last winter I drove my Prius cluelessly with similar results. One fill-up (mid-February) was 4.1 gallons, and all fill-ups for six months were less than 7.5 gallons. Don't let it get to you; just fill up at no less than two pips.

As a guess, I'd suggest you check your tire pressure if you haven't already. Among other things, cold weather causes tire pressure to drop significantly, which affects fuel economy significantly. Set front pressure to 42 psi and rear to 40 psi. See if that helps.

 

For the warning indicator to illuminate, pressure must be 25% under the minimum. Besides that be extremely dangerous (hence the federal mandate for the warning), it is a major impairment to MPG.

In other words, PSI should be at least 33. Your tires are around 25.

Bump the pressure up to at least 42 PSI front (40 PSI back). You'll be quite surprised by the change. I've been running mine at 44 PSI for over 6 years now.
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Grill block is pipe insulation from Lowes or Home Depot...2 six ft strips is a good start ($4.00 and plenty of good examples are here on PC) and engine heater can be ordered here on PC Shop. Make sure you have a GOOD tire gauge and use it religiously.
:welcome:

 

Overall I agree with all the suggestions and also have a couple of way out ones. My theory: The bladder is relatively stiff, even in summer and I truely believe that it can be streched to what should be its normal demensions. So when the attendant pumps gas and it stops at 6-7 gal tell him to keep topping it up slowly. You will find that you can get at least two more gal in the tank. It is sort of learning to accomodate to its capacity. Another way out suggestion is to fill your tires to at least the sidewall pressure, 42-44 I forget how the OEM is marked 44 I think. Believe it or not some posters pump the tires up to 55-70lbs. They do this not only for mileage ( which helps ) but, also for longivity. The OEM tires can get 40K miles instead of only 20K miles. You will have to fill and check tire pressure yourself, all the tire people have been programed. Test drive after filling tires, check the stabilty, if the stability is good put more air in! Of course let off the gas every time you approach a red light. See what you have to to do get the HV battery into the green state. It really does take a long time for the Prius to get broken in and get good mileage, it takes the owners even longer. I consider my 05 just breaking in and I have 66000 miles on it.

 

Maya, how long are your trips? Usually the 1st 5 minutes is at 25mpg. My 2nd 5 minutes is at 50mpg. During the winter I am lucky to see 25mpg during the 1st 5 minutes and can get close to 50mpg on the 2nd. I also keep the car on & locked when I run a quick errand. If the car is going to stand more than 10 minutes then I turn it off. This prevents the engine (ICE) from running during start up just to warm everything up.

Increase your tire pressure in increments and stop when you are not happy with the ride or handling. I stopped at 45psi because the car starts to feel a bit squirrelly. IMO, the people recommending low tp are the people that want to sell you replacement tires. Soft tires wear faster. The tire isn't overinflated as long as it is still flat (deformed) at the bottom. Tires lose 1psi for every 10F drop in temperature.

I keep the temp set at 72 and the fan at the lowest 2 speeds.

Last winter I managed to increase my lifetime average. This winter is colder but still expect to hold 50mpg.

 

Not going to troubleshoot your problem, but feel bad for ya ....

just for the record, here in SF Bay Area with 40s - 60s F Winter temps ...

I'm averaging about 54 MPG on the display this tank, ~ 50 last tank. Just normal, combinded driving. This car just blows me away in fuel economy.

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I hope you get yours resolved.

 

Be patient, you'll get there.:cheer2:

 

IF: You were driving almost any other car, your mileage would be worse!:cheer2:

 

That is strange.

 

The magic speeds during warm-up are30-40, here ( CA ) my car warms up so fast that I can achieve stealth in about a mile Stealth = no arrows, barring that, next stage is battery use only, unless the HV is in the green, that stage is hard to maintain. Any downhill, use to your advantage, either in stealth, battery draw or battery charge, either by slowing down for a light or with engine assist. Even with engine assist, the HV should be charging. Unless its in the green, then try to use that charge. The ideal procedure is 3/4 of the time free energy versus 1/4 time, using engine. Except freeway, then the rules change, ie: use CC. Overall CC is good, but on surface streets the driver is smarter. CC cannot see ahead. The main factor is always Topography. Hill up OR hill down.