MPG decreases from 52 to 43? PLEASE HELP!

Has this happened to anyone and did they have any proof?

 

I don't think any of your comments above are based on facts. Many people are well into the 100k to 200k mileage range are are still seeing 50+mpg, myself included. To put it simply, there is something wrong with your car. To flame all hybrids in general makes no sense just because you are having a problem. Maybe you should visit another dealer? As usual, your mileage may vary.

 

This sounds almost identical to what I am seeing except I got my car in July 2010. But around October the MPG dropped from 49-51 to 44-45 and as of last week (beginning of Dec) it is 42. The temp has dropped only since Thanksgiving so the issues I saw in October were not because of winters temps. I took it in to Toyota just before Thanksgiving and they said nothing was wrong and blamed my missing wheel covers. I put them back on and it is still dropping, but I think now it is temp related...just curious about what suddenly happened in October.

 

That's about the exact same pattern my MPG follow. I've had the car since June 2009 and have about 17000 miles on it.

For me, there was a hit to FE in Oct/Nov due to temps going gradually lower and probably the transition from summer fuel blends to winter blends. This could also account for your decrease.

I also noticed my PSI in the tires is down to around 32 all around from lower temps. I'm too lazy to increase it since I plan to toss my winter tires on this weekend. You may wish to check that, also.

 

I'll letcha know. As the G3 goes into it's second production year, and this years models continue to rack up miles, it will be interesting to see if there is more MPG grumbling out there.
I'm at 55.7/403/41 (mpg/miles on trip/average speed) now at 3K. This is without hypermiling 'techniques'---but the weather has been 40-50 degrees down here, and I'm not sure which of the 40-something different fuel blends we're being sold.
Like I said....I'll letcha know...

Good Luck!
Hope you get some relief!!

 

My tire psi was at 38, now they are at 40 psi. Let's see if this makes any improvement.

 

It's amazing how all these threads about falling mpg's always pop up this time of year, yet the posters insist it has nothing to do with winter!

 

This is my first year with my Prius and one thing is for sure. The engine runs a lot more when it's cold out than when it isn't. I'm not willing to turn down the heat and I'm getting 43-44 MPG which is way better than the 25 I was getting with my prevoius vehicle. I'm guessing that spring and fall are going to be when I get my best mileage. Not willing to shut off the AC either in the summer so I'm sure I'll take a hit then as well. I'm also not willing to worry about tire pressure and oil viscosity that much so for me, the lazy Prius driver, 43-44 MPG in the winter with climate control set to 72F is pretty darned good.

 

I'd love to get my hands on one of these cars getting low mileage.

Cycle the emergency brake on and off a few times
Clean or replace the engine air filter
Clean the cabin air filter
Change the battery, get a Optima yellow top(with fit kit)
Check engine oil level (2/3rd's up the dipstick)
Check air pressure(skip this if your run Nitrogen)
Get a Scangauge 2 and check for any error codes
Drive at the speed limit...

 

Clean the cabin air filter

What in the world does the cabin air filter have to do with MPG. ???

My 2010 III gave me the best mileage on the dealers gas. For that tank I was seeing 55 MPG....that has dropped to 42 MPG. I now have just over 5K miles on the car. With cold temps now, I don't expect any better MPG,,,,really don't expect any better at any time.

Just the way it is. !!!!!!! Still the best mileage car on the road today.

 

Welcome to winter, new Prius owners. There are a couple of things that can be done to lessen the MPG hit, but they all take effort or a bit of discomfort:

1. Use an engine block heater
2. Block the radiator vents
3. Wait for the ICE to warm up before heating the cabin
4. Try to combine short trips so that the ICE is not starting out cold so often.

I do 2 - 4, and keep my fuel economy just above 50 mpg in our moderate winter climate.

 

Not as bad though, probably. AC is more efficient than heat, per amount of energy moved. Not sure what the efficiency of car units (or the Prius in particular) is like, but home AC units move about 3 units of energy for every unit of energy consumed. This is because they are simply moving energy from one place to another - in this case, from inside your car to outside your car. It takes some energy to run the compressor to get that to happen, but this is significantly less than the amount of energy actually being moved.

Heat, on the other hand, is typically not handled in this manner. In the case of your car, the gas is burned, then the heat from this process is used in the heater. Most homes either burn some fuel (wood, coal, oil, natural gas) or have electric heat (which just uses the electricity's energy to heat the house, rather than doing something more useful like moving larger amounts of energy around). In any case, the heat energy that is obtained from this is less than the amount of energy put into the system.

There are some heating systems that work as if you put your air conditioner facing the wrong way; these are usually termed as heat pumps. Unfortunately though, they tend to not work well at very low temperatures, which is when you want the most heat.

Anyway, the point of my post (before I get too far off this tangent, even though I'm well off-topic already) is that cooling from 90° to 70° is probably going to take less energy than heating from 50° to 70°, especially if, in the cold case, your car is desperately trying to warm itself as well. On the other hand, if you're on the highway and the engine's running all the time anyway, heating might be more economical once the engine is warm, since there's probably an excess of heat, and there aren't many other uses for the waste heat in your car.

 

To save energy, the Prius has a feedback control climate system. This avoids running the heater too high, or the AC compressor at too high a speed that is needed, and both for longer than is required for the operators goal. The fan and compressor speeds will speed up and slow down as the themal demand varies.

If the cabin air filter is clogged up then there will be less air flowing through it for a given fan speed. So, the fan will needed to be ramped up longer and stronger to get the same thermal transfer.

This effect is bigger in the AC system, as the compressor and radiator fans are running, besides the cabin fan.

 

If the cabin air filter is clogged up then there will be less air flowing through it for a given fan speed. So, the fan will need to be ramped up longer and stronger to get the same thermal transfer.

This effect is bigger in the AC system, as the compressor and radiator fans are running, besides the cabin fan.[/QUOTE]

I think this only pertains if the climate controls are set to "AUTO" Do you agree ???

 

Hi Troyroy,

Yep.

But do not think running the system manual, and not paying attention to it, will use less energy.

 

You are not using the same gas as the previous gas is burnt already. What I'm saying is if your local gas went to 10% alcohol like it did in my area in May 2010, you have an instant 5% (or more) hit on MPG. There could be some other issues. Maybe the oil change place gave you cheap 5W30 oil instead of the 0W20 one? Maybe you driving shorter trips? Etc, etc.