Pulse and Glide

Coming home from Snohomish today, I decided to use some slightly different driving techniques to see what I could do in terms of maximizing my tank efficiency. I had just filled up earlier in the day about an hour before departing, then driven about 5 miles to my parent’s house.

I didn’t decide to try anything until about halfway home in stop-and-go traffic in Tacoma. There are two driving techniques that are not unique to the Prius but that are particularly useful in increasing MPG: pulsing and gliding. The best explanation of this comes from Yahoo’s Prius-2G list (specifically, this message):

Think about riding a bicycle. Pedal until you get up to speed, and then just stop pedalling
and glide. When you slow down, pedal again, then glide again. That is exactly what “pulse
and glide” is.

One fine point – the glide. Gliding is possible mostly at less than 40 MPH, when the
engine is warmed up and the battery charged. You mentioned taking your foot off the
pedal and coasting. That is a start. While watching the “energy” screen, after you take
your foot off the pedal, with a very light touch step on the pedal slightly until the arrows
all go away. That is gliding, with no electric motor, no gasoline engine, and no
regererative braking. You will notice the car glides a good long way.

Switching to the energy screen and doing some trial-and-error, I managed to do a couple of fairly long sustained glides under 25MPH, though, due to the activation of the internal combustion engine at higher speeds, the ability to glide becomes progressively harder. I did try, and managed to do it for a split second once near 55, but it’s not easy to sustain.

By the time we got back home, we had attained 62.4MPG with some heavy boxes in the hatch area and 89 miles driven. Not bad, but that MPG number would be more impressive with a higher number of miles. My goal for this tank is to beat the best displayed MPG of 55.8 for a single tank by at least 2.2MPG, resulting in a 58MPG screen or better. We’ll see if this happens – so far, an average tank takes me a little less than 340 miles per tank, with a wide range between 207 and 464 miles on a single tank.

I have to point out, however, that my refill policy thus far has been a little panicky, as I haven’t always waited for two bars on the gauge — this is my new policy and I don’t intend to break it if I can help it. Thus, my average tank length will likely increase over the next five to eight tanks or so as I’m careful to make sure that that policy is followed.