Fuel economy dropping.

Here are my first comments. More may come later, and be aware that some of us may give conflicting advice.

I'm in the same area, but was traveling elsewhere the first half of the month so cannot comment on what the home weather was then. The current temperatures hurt MPG. If you had much rain or wet road while I was gone, that would also hurt.

Grill Blocking helps in cool weather, and I actually keep some grill block in place most of the year. But I don't recommend this without some sort of engine monitor (e.g. standalone Scangauge, Torq app for a smartphone, Garmin with a bluetooth OBDII dongle, etc.) to display engine temperature.

I hope F8L can chime in about the rolling resistance of this model, whether or not it is LRR. Being fairly new will temporarily hurt MPG until they wear in a bit.

Skip the egg on the gas pedal, that idea is too simplistic. The engine's efficient operating zone still allows 'brisk' acceleration (that doesn't mean anything near floored). This is also true of most non-hybrids, which led to the development of 'pulse and glide' as a fuel saving technique.

And while you are getting used to the car, don't try to stay in EV mode, let the car make its choice. It is too easy to overdo it and actually lose ground. After you get a good baseline of what the car will do itself, then you can try to improve upon that.

Using EV mode means using energy that has been laundered through more energy conversions, and therefore scalped by more energy loss mechanisms, than using energy direct from the ICE. And in most cases EV energy will eventually get replaced by gasoline energy, so it isn't free, so it often pays to minimize EV.

Use EV only where the power needed is low, not enough to justify the high overhead cost of running the ICE. Most acceleration does not fall into this category.

Hypermiling guru Wayne Gerdes recommends using EV to accelerate from a stop up to only about 15-17 mph, then switching over to the ICE for the rest of your speed gain. This applies only on flat ground, switch earlier on up slopes. Many of us who are not competing for maximum MPG score, or who must deal with impatient traffic, also use gas from lower speeds and can still get great results.

Coasting and light braking -- DWB, Driving Without Brakes -- helps enormously.

This setting will hurt a bit if you spend any time sitting at traffic lights during engine warmup. Unless window visibility demands otherwise, I tend to keep the heat down, then turn it up into the upper 60s after the engine warms.

Pick one of the trip meters to use for daily MPG scoring, resetting it every morning. This provides more rapid feedback about what works and what doesn't, compared to resetting only when you fill up. (Use the other trip meter for gauging whole tanks.) It also highlights the MPG cost of engine warmup, you will see hideously low MPG for the first mile or so, then it will gradually increase as the trip lengthens. The score at the end is what matters.

 

I would say Yes to both for at least a full tank or two, and establish a baseline for future comparisons. Then you will have a reference point to help judge what fails, what makes no difference, what works well, and what barely works and isn't worth the time and effort.

Changing weather will add a bit of complication, but warming and drying trends will help.

If you had a Gen3, I think you would find that any gasoline acceleration staying within the ECO range of the HSI display would work fine, and that even going well in the PWR range (but not pegging it) would produce 'good enough' mpg for most noncompetitive purposes. But Gen2 doesn't have this screen , and its better efficiency doesn't go to quite as high RPM as the Gen3.

Do note that the 50 MPG EPA rating doesn't apply to the Gen2, or even the Gen3 on the highway. The Gen2 is rated 45 highway, 46 combined.

Pulse and Glide doesn't fit with heavy traffic on flat highways. It does work on empty roads, but most of us don't bother, especially in a hybrid. It produces greater return in traditional nonhybrids, especially with manual transmissions. I generally save it for rolling hills where a terrain-coordinated P&G (pulse uphill, glide downhill) is fun and effective.

City traffic and congested stop (or creep)-and-go on the highway is another matter. If you can get reasonably coordinate your P&G cycles with the traffic movement or traffic light cycles, it can work wonders. Prius MPG can start climbing substantially where non-hybrid MPG would collapse. But getting that coordination is the tricky part.

 

It won't be the best, but it should be quite good, and it will also be a necessary reference point. When you start gaming it to do better, that reference will be a minimum, letting you know when your methods are unintentionally sabotaging the quest for higher mpg. It is surprisingly easy for newbies to do worse than the car will do on its own.

I no longer commute. Here is what my 2010 did for its first two years, showing the strong impact of weather:


This was mostly various road trips for the first 10k miles, then commutes for the remainder of the graph. Commutes (32-40 miles round trip, depending on route choice) were a varying mix of off-peak highways trips (lower mpg due to speed), and on-peak congestion-avoiding back streets and arterials (higher mpg due to lower speeds and lots of gliding).

I haven't yet extended this graph to show the 2010's final ten months, nor the 2012 results. Note that this was a Gen3, which is rated 4 mpg better than your Gen2.

 

Chances are the longer you have the Prius, the more you will see that the numbers will flop back and forth when comparing MFD readings to the actual hand calculations per fill up. What really tells the truth is by measuring the MPG over several tanks. That is where Fuelly.com will really help you. The MFD is really only an estimate and at times will fluctuate due to a lot of factors.

Take a quick look at the record's on my signature for Fuelly. I have tried to note the MFD reading's for the past several fillups. That should give you an idea of how the 09 we have is reading.

FWIW, I have found that hilly area's do affect the MPG and will cause it to drop. Here in Texas if I drive strictly around Houston where the road is concrete and is virtually flat I have very little trouble with low mileage. But if I go to East Texas or the hill country (Austin and west) I will notice that I will lose anywhere from 3 to 5 MPG. I have a feeling that what you are seeing is what I call the "cold weather blues". The Prius MPG will vary considerably due to temperature and humidity. When it gets cold, the mileage will fall off. Again, you can see that in my Fuelly. I have tracked it for over a year now so it should give you a good idea of how the Prius will work. When you throw in the hills you have it comes as a double whammy. The nice thing about a hill though is this. If you can go up the hill starting out at a brisk speed and then let the speed drop slowly as you go up to the crest without impeding traffic, and then coast or glide down the other side you should see a slight improvement. If you use cruise, the engine RPM's will rev higher using more fuel to maintain the speed you have set. But if you use the foot feed and let the speed drop a little the engine RPM's will be less. (less fuel burned - higher MPG) There is a thing called "warp stealth mode". That is when you are going faster than 42 miles per hour and the MFD show's NO arrows in the energy mode. You don't see it often but you will if you watch the MFD when you are using the cruise and going down a hill. If you can warp stealth mode going down the backside of the hill, that will help some too.

Keep studying all of the tips and tricks you can apply for better MPG, but remember this. Even when the Prius deliver's it worst mileage, it is still a lot better than a mini van or a big SUV. I remember all to well the Mazda MPV we used to have. On it's bad days, we were lucky to get 14 MPG. Now that we have the Prius, we are averaging 47 MPG overall.

One other thing, since the Prius is very efficient for the most part suttle things will effect sometimes drastically. Fuel quality is one of them. You may not notice it on a big truck, but with the Prius you will. It has been suggested here on PC to run gas that is from the Top Tier Group. IMO, I have found that if I run Shell 87 octane I get a little better mileage than if I run cut rate gas from the Mom & Pop places. Here is a list of retailers that are in the top tier group.

Top Tier Gasoline

It will be warmer and drier soon, then your mileage should improve. Good luck to you and enjoy your Prius.

 

I believe the Gen2 models generally had a fairly accurate mpg screen, not the 'optimistic' screen reading typical of Gen3s.

However, Gen2 also has that inconsistent rubber bladder in the fuel tank, which throws off the tank-to-tank comparison. So, as 'dorunron' said, average together a series of tanks. Fuelly will at least give you a longer term actual mpg, I don't know if it can average your screen readings for comparison too.

 

After you get a baseline MPG without trying anything special, then start reading up on hypermiling over at CleanMPG.com. These were the most relevant threads for me:

Beating the EPA - The Why’s and How to Hypermile

Pulse and Glide plus Warp Stealth in the Prius II for maximum FE …

Somewhat similar advice is posted in various places over here on PC, but I started out over there with a non-hybrid a year before buying a Prius.

 

+1

http://www.cleanmpg.com/forums/showthread.php?t=1224

This one also gives tips on "winter driving" for the hybrid's.

http://www.cleanmpg.com/forums/showthread.php?t=17560

 

You'll find that the prius is more sensitive to ethanol percentage than many cars. Try finding 100% gas (puregas.org) and fill up with that for at least 3 tanks in a row.

Also don't accelerate in EV mode above 10 mph, don't drive in EV mode over the longer distances unless you are going downhill. If you are driving uphill give it more gas, if you are going level you want to either push the gas like you are going slightly uphill or glide (make it so that neither electric or gas is used and you aren't braking, you have to keep your foot on the gas pedal to avoid regen).

If you are in repetitive hills (uphill then downhill, then uphill, and so on) you will find that you are better off at a certain speed on each hill, the length of the slope and the amount of altitude change will vary the target speed for efficiency. If the net effect of multiple hills is a loss in altitude you'll want to drive nearer to the speed limit / ticket area. If the net effect is a rise in altitude you'll want to stay below the speed limit on the uphill portions. If the rise is long term steep (long enough that your speed would drop to 0 if you didn't increase the gas enough) you just have to bite the bullet and stomp the gas pedal but if the length is shorter you can play the "driving with load" game of building up speed on downhill/flat sections and allowing your speed to drop on the uphill sections.

Just as an example I found that if I tried to avg 45 mph on a local interstate with lots of hills I got worse gas mileage on the downhill leg of a round trip commute than if I tried to keep the avg around 60 mph. Going the opposite direction I don't notice much difference so I go 45 if I want to save gas or 55 if I'm wanting to save time but the gas mileage is worse the faster I go on the uphill leg.

 

I can see that everyone has given you a very comprehensive list of does and donts. I encountered a similar phenomenom with our gen 2 and yes, the tyre pressures, the heater, the air conditioning, the winter fuel, the cooler ambient temperatures all come into play. My problem improved dramatically when I cleaned out all of my brake calipers. During the winter months, the roads also tend to get dirtier and that dirt collected in my calipers and gradually, my brakes started to bind more and more. An easy way to tell whether your brakes are binding is to touch the metal of your wheels at the end of a journey which includes no prolonged braking. I found that all four of my wheels were warm to the touch. I guess that the binding would become worse over time and my fuel consumption would get worse too.