Apparently I'm an Eco Driving Ace (First Tank MPG)

Congrats. Some people just have a natural knack for eco driving.

Do you mostly do your driving on surface streets?

Also your MFD vs Calc MPG spread is one of the smallest I've seen. Mine is closer to 2.5 - 3 mpg.

 

Highway = 55-60 MPH? There's a sweet spot in there that gets good mileage. If you pulled that MPG at 70-80 I'd be really impressed.

 

I got 54mpg on my last tank and the gage read 55.7, it seems the higher it gets the more accurate it is because I have 38k miles on mine and it has never been within 2mpg.

 

I find terrain to be a major factor. You can not recoup downhill what you lose going uphill.

 

I don't know about that... I consistently go up a 1000 ft hill that is 6 miles long , and always end up with the exact same mileage I started with. Usually about 60 mpg. The trick is to set the climb at 20 hp max, and the downhill run on all electric, never exceeding 45 mph. I will end up with the same battery level and the same MPG I started with. Surprisingly it does better than my Insight 1 did on the same run, even tho the Insight consistently got lifetime mpg of 5 mpg better than the Prius.

 

What I have noticed today that I think contributes to your on screen computer mileage being different than your actual mileage is that the MPG thing in the car keeps going even if you are stopped at lights. I sometimes leave on my 5min consumption when I am sitting at a standstill for a long time, and it just keeps adding up (obviously maxed out at 100mpg).. That is what I think ultimately makes for that 2-3mpg difference from the cars computed, and what we computer when dividing mileage by gallons in the tank. Cause my best average according to the car was 55.2mpg, but actual was 53.5mpg. Just something I noticed. Also if you hold down the DISP button while on that 5 Min Cons screen it will give you your 1 Min Cons so you can watch it without having to wait so long.

 

Push that button just to the right of the steering wheel and ICE will start making a low humming sound. Now your Prius will also go uphill, but your FE will drop a little when you do. :welcome:

 

Ted, won't try to explain how you achieve that -- too many variables with the measurements made by the metering system, and the total energy difference will not be a great deal anyway, but physics is physics. It takes a certain amount of energy from the drive system to go up the hill. You gain potential energy (PE), but not as much as you spent getting up the hill -- no energy conversion process is 100% efficient. Going down the hill you convert the PE to kinetic energy or save it to the battery, but again no process is 100% efficient. In thermodynamics, you always lose -- it always costs more energy than you can get back. Hills always take away from your available energy.

 

I'd just to offer a small addendum. The conversion of PE to KE and KE to PE is 100% due to conservation of energy. No thermodynamic losses there.

The reason fuel economy suffers in hilly terrain is that each situation requires us to use the ICE and battery differently than from flat terrain.

For instance, we may be able to coast (glide) more in flat terrain, such that pumping losses, friction, etc. while the ICE is on is not encountered as frequently. This is more apparent in the Prius since the PSD can essentially decouple the ICE.

So in hilly terrain, we may opt to use the ICE more continuously, even though average power output is the same, so losses are a bit higher.

Also in hilly terrain, we may also have higher peak power demand, forcing the ICE to run less efficiently and thus burn more fuel. We may also require power boost from the battery pack, where conversion losses are great.

I've used the strategy of pulsing downhill (overspeeding) and then pulsing uphill (losing speed), with the ECO indicator light on. This averages the power demand so that I don't have to go into the power band. Anectodotally, this has given me better overall round-trip results than powering agressively uphill, then gliding downhill (with speed more constant on both legs). So it seems keeping the ICE in its efficiency sweet spot is the key.

 

I will be filling up for the 7th time today and am delighted to be averaging slightly better than 57 mpg since I bought the car. I drive in a way that maximizes mileage and enjoy the game. Today we will make our first road trip (around 400 miles round trip) with some healthy inclines and declines. I am anxious to see how the car performs getting my kids to their Grandparents. Enjoy and cheers to having a car that helps pay for itself.

 

This is my first post. I have a couple of comments and a Question. The comments are,so far i am very happy with my purchase(just got the car about 3 weeks ago). I bought a new 2011 Prius two. We added a Kenwood radio with Garmin Navigation,Blue tooth and rear camera. This installed was $1300.00,works great.I plan on adding the fog lights,rear mat,and mud flaps.
MPG were about 46 on the first tank and are about 51 now. We live at the top of a steep hill,in Western Pa.l. The hill is a little over a mile long with several 90 degree turns,some almost make you stop.I have not taken the car on a trip longer then 25 miles yet. But on the short trips to town I always lose MPG coming home. I am convinced If I lived in a state like the great state of Kansas that has lots of flat roads I would achieve better MPG.(even 50 miles west in parts of Ohio)
My question is this,I have noticed that some say they do not drive in Eco mode but drive in Normal mode. On my new Prius there are 3 modes EV,Eco and Power. Is Normal mode something that is in older cars or am I missing something?

 

Short trips are likely to result in lower MPG. It is not unreasonable to be unable to break 40 mpg on a 5 mile trip. Similarly, going up a hill will reduce your mileage, until you gain it all back. What goes up must come down. Unless you waste all of that energy using your friction brakes or you saturate the battery. My suggestion is to bunch up your errands so you can string together your trips to make one longer trip.

The mode is just how the car responds to the pedal position. It doesn't actually change anything under the hood physically or electrically. In ECO Mode, you have to push the pedal further to get the same response as in Normal or Power Mode.

If you want, I can elaborate further on strategies to achieve better mileage when your destination is at the top of a hill.

 

Wampum, "Normal" mode = absence of mode (nothing lit up in terms of ECO/PWR/EV).

 

Not sure I understand what you're saying. But, you cannot regain all your PE going down a hill. The simple fact of wind resistance negates the possibility. Of course energy is conserved, but all the PE does not get converted back to KE for your car. You are giving KE to a lot of air molecules. The thermodynamic losses also are present. Assuming you used an energy source to get up the hill (ICE or battery), the energy conversion to KE is not 100% efficient. So, it cost you more energy than you gained in PE. Going uphill is a losing proposition. I think all state legislatures should mandate that all highways be flat (lol).

 

That is all true, but as long as you keep to the 20 hp (ideal BSFC) , you are doing the same or better compared to driving along on a flat, pushing air. What happens is that you run the engine at a higher efficiency than you would driving on a flat at half throttle. So you put into PE energy at a higher efficiency, which you get out at 100% when that PE gets converted to KE on the ICE off coast down the hill. At least I think that is what is happening, all I know is I can repeat this and always end this run ( 12 miles round trip - 1,000 ft up and down) at the same or better mpg than I could do on the flat. My average MPG ends up the same as it was or higher. Typically 58-60 mpg depending on outside temp.