When I first got this hybrid I set the cruise control to 53 MPH and never went over that.
You might ask, "Even when passing?"
I would answer, "I've learned to pass without slowing down or speeding up, just be patient and wait for an opening, or plan ahead a few seconds so you are don't have to change lanes at the last minute."

Well the MPG I got from going 53 MPH wasn't good enough so I've been going 50 MPH for the last 6 months or so.
That's why my MPG went up to 67.8 MPG on the last tank.

Actually I'm trying something new now.
I'm trying 48 MPH for this tank.
I've gone 110 miles so far and have averaged 70.7 MPG.
I was under the impression that the optimum speed, for MPG, was about 53 MPH.
Now I suspect it is closer to 40 MPH but that would be suicide and ticket time.

I think a 70 MPG tank may be in my future.

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.

Would warmer weather and other factors be playing a part in better MPG?

Certainly, warmer temp makes a difference!

But in the last 2 days my MPG is about 4 or 5 MPG higher driving the same route I've driven for 4 years of hypermiling.
The temp has not beendifferent the last 2 days.
The only difference is my max speed has been 48 instead of 50 for the last 110 miles.

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.

If you get a chance, can you run a series of one hour tests at 10 mph increments from 30-70 mph?

In a perfect world, it would be 30 minutes in one direction and 30 minutes in the reverse. Make sure the wind and temperatures are recorded and if possible, w/o the AC?

We can use this data to plot an MPG vs. MPH curve for your vehicle. Once you have a baseline, it becomes a lot easier to look for:

• knee in the curve - places where one side is great and the other not so good
• effects of tuning efforts - thus oil, maintenance and tire changes can be quickly checked against the baseline

Now in a perfect world, we'd also want to see the low-end mapped in 5 mph increments, 10-30 mph. This is usually handled best by finding a close loop, like a shopping mall parking lot, to 'do the laps.' If doing laps, only 30 minutes is needed to make sure the MPG reading is reproducible.

GOOD LUCK!
Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Wouldn't those tests waste gas?

Ironic.

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.

kenny, don't let 'em deter you. i am finding the same thing. i had 70 MPG for over 150 miles on my current tank over the weekend. the difference? i wasn't going to work and was driving about 45 MPH on the back roads. i went the same route both days, kind of an up and down road, so equal down and up hill, since i ran it backwards on the way home. i really find the sweet spot to be between 45 and 48. adding back in going to work on the 4 lane where i at least have to do 55, often 60, and battle a head wind, i have dropped the entire tank back down to about 65......

good work!

Best fill 66.7 MPG, best tank 801.5 miles


laurie, central minnesota

Incorporate your testing in ordinary trips you'd normally make. For example, my first set of charts came from picking up my 2003 Prius in Ft. Worth Texas. I simply broke the 810 mile journey back into ~2 hour segments at different cruise control settings. For my city commute, I simply choose routes that allowed me to run the car at different speeds. For high resolution data, I use a flat-stretch at Marshall Space Flight Center on the weekends when I take my dog for a run down by the river (my dog is my lab tech.)


Engineering uses tests like this to get data we can use operationally. Since the operational use is typically 100 to 1,000 times more frequent and of longer duration, the 'test overhead' disappears in the grand scheme of things. Best of all, the insights can lead to operational savings that more than pay for the test overhead. After all, you run the test once but often drive daily.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Kenny - thanks again for the great info. I think you all ready are running tests by dropping your speed. At 64mpg lifetime you probably know when something is working better...

Bob - I have been meaning to run these series of mph vs mpg tests for a while now, though not really an hour per run, but maybe a few miles (minutes) up and back on same stretch of road at say 35-65mph. Would plan to replicate each up/back run 3-4 (or more) times to see the effect vs noise (weather, soc start/end, etc...). When I get to them I will post results.

Funny, if "peak" mileage turns out to be at say 45mph, then is it best to "speed" a little in a 35mph zone - assuming the next slow/stop area is far enough down the road?

The way to handle short tests are to run lots of them. Then look at the results to make sure they are reproducible and average the results. But having any data is better than no data as long as the test environment is documented.

To answer your question, I avoid 42 mph like the plague. I either speed up to 48 mph or slow down to 38 mph. It depends upon the road conditions and traffic.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Speaking of 2004-2007 Prius, the best fuel economy is achieved at 20 mph according to Wayne's research.
http://priuschat.com/index.php?showtopic=15285&st=32

Ken@Japan