Gas Pip Lines

You are welcome.

The Prius approach to battery management is conceptually fairly simple. It tries to optimize the use of the engine by running the engine at efficient loads and speeds. To do this, it uses the battery as a booster when needed, and to store excess energy when available. For example, when creeping along in stop and go traffic, it doesn't make much sense to run the engine if battery power is available.

On the other hand, if the Prius finds that it needs to run the engine in this situation, for example due to a low battery or needing heat for the cabin, then it might as well run the engine harder and get it up into a more efficient range. To do this, it runs the engine harder and uses the extra energy to charge the battery. This is one of the reasons that green battery bars are more common in the winter. The engine has to run often to keep the car warm, so while it is running it charges the battery.

Under heavy acceleration, it's more efficient if the engine doesn't have to run wide open. Before the car will do this, it tries to draw power from the battery and boost the acceleration with the electric motor. If it needs more power, or has to do this too long, it gives up and cranks the engine wide open, making that horrible racing engine sound.

Just think of the battery management as a balancing act. The controller wants to keep the battery in the blue bars, but will compromise as needed for better efficiency.

Tom

 

Amazing, on my car when I have gone 180-220 miles I am down to two or at most three pips.

 

It's not that hard to understand. You are over-thinking it. The main thing to understand is that the fuel pips are non-linear, or to use non-mathematical language, they are uneven. Don't expect them to disappear at the same rate.

Almost all automobile fuel gauges stay at the full line for a fairly long time, then fall more rapidly after that. The reason for this is that it's not very important to know that you have a full tank, but it is important to know when your tank is almost empty. Since the fuel gauges are relatively simple and inexpensive devices, the auto makers build the error into the full side of the gauge where it doesn't hurt as much. Also, of course, the miles per pip varies with your miles per gallon.

As for you mileage variation, that's fairly common too. Some minor change has lowered your mileage. It could be colder weather, one or two short trips, a change in fuel formulation, or any of a dozen other things. Don't worry, it will come back up eventually. Make sure to keep an eye on your tire pressure, as this is one sure way to kill mileage.

Tom

 

That's a personal choice. Obviously the manufacturer's recommendation is the safe choice. That said, many drivers on this board use higher pressures. I run mine a few psi higher than the recommended setting, but I don't go up to the max like some. It's important to keep the front tire pressure two psi higher than the back. This helps compensate for the extra weight on the front end.

If you want to experiment with higher pressure, try going up about four psi and see how it feels. If the ride becomes too noisy or harsh, drop back down.

Tom

 

I understand what Tom is saying, but still, I'm like Tassee -- her mileage really does seem low for the pips to disappear regardless. My first pip lasts until about 130-145ish and on the way home this evening only the 2nd one was gone and I was around 200 miles since fillup. Could there be something with the bladder that would cause such a discrepancy?

 

There is more gas at the top of the bladder then the bottom.

 

Tassee, you are asking a lot of good questions. The answers to many of them are in the homegrown Prius owner's manual : John's Stuff - Toyota Prius User-Guide

and searches of the PC forums. Using the Google search in the search tab up top works well or you can do the same thing by googling a subject and adding priuschat.com to the search phrase. Adding the .com site tells Google you want to concentrate your search to PC or another website.

 

Right, but she was speaking about the top -- the first pip would disappear after just 77 miles then the 2nd after another 22, and then was down to half-tank with low mileage. Regardless of how the guess-gauge works ... it seems like something is wrong for the gauge to go down that quickly (?).

 

Perhaps there wasn't as much gas in the tank that time?


This is an artists illustration of the gauge.

 

Ah, thanks for the illustration. I guess that's it then. Maybe she got the shut off early or something. Sounds like she had it happen several times like that too.

 

Marcia - No need for concern on your part. It sounds like you are doing very well with a brand new car. Don't worry about what everyone else is getting for MPGs or miles on the first pip. If you were to ask those folks what they were getting for mileage their first 2,000 miles, you'd happily hear that most of them were just where you are today.

WARNING! Don't push it! You can cause serious damage to the Prius by overfilling. Fill it up slowly (I lock it on the first notch, when possible) and only add a little bit more, if any. I've had only one fill go over 10 gallons, and I wasn't happy to have gone that long with a flashing pip! I'll normally fill up at one or two pips, and I never worry about running out of gas.

Something may have changed. I've noticed it. If you have an early morning commute, you'll notice the cooler temperatures at the start of the day. This requires a longer warm-up for the car, and I've seen my mileage plummet these past two weeks. This doesn't mean anything for those folks in LA or Florida, but it means quite a bit to those of us in the North. Your mileage will taper off through the Fall, it will drop precipitously during the Winter, it will climb through the Spring, and it will skyrocket during the Summer (depending on your need for A/C).

I wouldn't worry in the least, Marcia. Enjoy your great car and the fact that you are getting x times the mileage you were getting in your previous car.