Saturday, May 10, 2008

My Thousand Miles on the Prius

In the Mike Mahaffie Prius owning tradition I have taken a picture of a "significant", because of our base 10 system, odometer reading.

I got the car at 1 mile and have now driven 1000 in almost two months. I still really like the computer and other gadgets, especially Bluetooth pairing with my cell phone and voice actiated commands. I only rarely miss the turbo of my last car. I have tried to make a game out of getting the best gas mileage I can but I have a ways to go, only 42 mpg so far. Only two fillups so far as well.


Paul Smith Jr. said...

Only 42? I've gotten that in a 1999 Honda Civic. Not around here, though, which might be the difference. I've done it a few times driving the mountains in Vermont.

Mike Mahaffie said...

Are you going by the mileage gauge built-into the Prius, or the old-fashioned way, doing the math at the pump? The Prius has a flexible-bladder gas tank, so you can't be sure that each fill-up is the same amount. Therefore, mat that the pump is not as accurate.

I use the built-in gauge and I reset it after each fill-up, which gives me a more immediate read.

There are driving techniques that one can use to help maximize gas mileage. A steady, even approach to speed is the key (as it is for a traditional engine). One can also learn to accelerate briskly and then ease-off the gas just a tad to "feather" t into a low-emissions, low gas-use mode. Gliding deceleration into stops help as well.

I'm generally getting between 50 and 52 MPG just now, though the worn-out status of my current set of tires may be propping that up. Over the long haul, I usually get between 48 and 52 MPG per fill-up.

Bear in mind that the real value of the Prius is that it is ultra-low emission. Saving gas is a by-product of the clean-air benefits of driving the thing.

Richard said...

Paul, Do you still have that car? I will trade you. Just kidding. Was it 42 in city driving? Fortunately my drive to work is around 6 miles, but that means the car barely has time to warm up before I turn it off.

Mike, 42 on the screen (sometimes 45) and calculated from usage. I have heard about this gas tank bladder thing and its "effect" on the mileage calculation. If I drive X number of miles and then fill up and get Y gas then my mpg is X/Y. But that is assuming that Y is the gas I used which assumes a constant gas tank size, I just replace what I burnt. Now you are reminding me that the gas tank size changes on every fillup which besides aggravating me, makes any check of the computer on the Prius impossible. I assume the computer knows the flow rate of gas and the distance traveled which depends on knowing the revolutions of the tires (which the computer measures)and the tire radius (which the computer assumes), both subject to their own errors.

It seems to me that the two important things for me are the miles I drive (if I don't drive them I end up short of my destination) and the gas I pump and pay for. If I were to calculate $/mile I wouldn't use the computer I would add up my receipts and divide by miles. So in short I don't know the answer to the problem to my satisfaction.

You are definitely right about the emissions, lower for less gas and lower for more efficient use of the gas engine.

Mike Mahaffie said...

Good points, Richard. I assume that the in-dash gauge is not 100% accurate but I figure it is relatively constant, so I can use it as a measure of my ability to drive in a way that saves gas and lowers emissions. I'm not as concerned about gas usage as I am about emissions and so if I can see that I am maximizing the one and reducing the other, over time, I am content.