Wednesday, April 13, 2011

Fill-up, Tuesday, April 12, 2011

478.1 miles
7.567 gallons

63.18 mpg
3.72 L/100km

Wentworth's complete fueling history

Understanding the numbers

You may be wondering why I "only" get low 60 mpgs or high 50 mpgs on my tanks when all my mileage pictures seem to be easily up in the 60s or 70s (well, at least I was wondering!). While I have lots of nice shorter trips, my other, longer commutes involve a series of hills and hard accelerations, as well as lengthy periods over the Prius glide threshold of 42 mph. One route I take twice a week is apparently net uphill, and while I can usually maintain 60 true mpg (as opposed to optimistic Prius display mpg) on the first leg of the trip, it can be tricky. The way back I can often get mpg of 62-66 mpg fairly easily, despite those same hills in reverse, and 21 stop lights to contend with once I get off the higher speed portion of the trip.

I also have a series of short trips for work that are unavoidable. I've estimated before that over the course of two weeks, they knock off a small 2 mpg or so from the tank. Not a big deal, but just enough to drag you down to 60 or below.

Three times a week when I leave the house, I head south - directly toward a huge hill that means I never get better than 25 mpg during the first five minutes, which kills the mileage for the trip from the get go. On these trips of 27 miles I use nearly 20% of my gas for the trip in the first 2 miles!

And of course, once or twice a tank you get crappy weather, and all the pulsing and gliding in the world won't save you from the wind and rain. At the beginning of this tank I had a miserable 55.8 mpg displayed (so probably 53-54 mpg in real life) over my longer distance commute in a delightful little bout of wind and rain Mother Nature had sent our way.

Trip o' the week

I loved this trip. Yes, I've gotten and can get better mileage on other trips, like the short trips where I just glide and EV most of the time, but this one is the most satisfying, since it's not at all pure pulse and glide land - half the trip is too fast for gliding anyway. There are hard accelerations from 0 to 50 mph, hills to climb from a standstill, some 2400+ RPM spots (pedal to the metal! well, not really, but maximum desirable warp, let's say) and after all that, the dreaded 21 stop lights.

The previous trip record for this particular route by the Prius display was 73.3 mpg. I knew I was likely going to break it right from the start. My coolant was still warm from the drive over, so I got into stage 3 very quickly and was able to glide/EV within a couple minutes of starting up. I waved a tailgating wench around me at a stop sign (no accusations of the Prius holding up traffic - I was already going 10 mph over the speed limit leading up to it), and warp neutraled it down a slight hill. At the next stop sign I did my new favorite routine, which is forcing the gas engine on to get to stage 4. After the engine turned off, on I went.

At the end of a road where I usually end up with mpg in the 60s, I was greeted with this:

Nice! The mileage wasn't going to stay there for long, since just after taking the picture, I had to accelerate from 0-50 mph quickly, and uphill. Soon followed another 0-50 acceleration (I had more time on this one and went EV until 20 mph). As soon as I'm up to speed, there's this great slight uphill that I can maintain 50 mph on getting 50 mpg. All the other cars on the incline around me were surely getting about 20 mpg or worse at that point - which is why every car should have an mpg display, but I digress :-)

Warp stealth, hill, warp stealth, hill, warp stealth, bridge, warp stealth, some burn and gliding as speed limit goes down to 40 mph. I slow to a stop to pay a toll - record mpg as of this point in the trip, nice!

Then 4 to 38 mph acceleration up a bridge, the killer - 2500 RPM to keep speed, then I was able to ease up to 2000 RPM somehow for the upper half, losing speed slightly.

After the downside of the bridge, I'm back to the 21 stoplight part of my drive. I remembered from the record in February that I got very lucky with all green lights, and realized that they would be the deciding factor. Things were going OK until one spot where I needed the ICE for safety where I would normally glide, and then got stuck at a complete stop at the worst light of the entire commute. It's halfway up a relatively steep slope, and I'm the first one in line, meaning a brisk acceleration will be needed uphill. I climb the hill at the green light, and try not to shudder seeing the numbers - 4 mpg, 5 mpg, 6 mpg (did you even know a Prius could get that low?? :-D). It shaved a ton of the average, and I was now slightly below where I had been the last time at this point.

I managed to scoot through the second to worst light (before an uphill) while it was yellow, salvaging the trip, and while I had to slow at other ones, only got completely stopped at one more.

Toward the end of the trip I went to town using EV where I would normally need the ICE, and it worked. Barely beat the record. 73.8 mpg display, Scanguage a more realistic 71.1.

The awesome part is seeing the improvement you've made hypermiling. I got stopped at two more stoplights than the last time, including the huge uphill one, and still managed to beat the record. Very happy!

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