The purpose of this test is to see what kind of mileage my 06 HCH will get on my ~27 mile commute (95% freeway) without any input from me; i. e., simply using cruise control. I'm curious to establish a baseline for comparison with hypermiling techniques (pulse & glide) that I'll try next and to see what the car is capable of for the average driver who doesn't use these techniques. I'm also curious about what effect speed has on mileage (with all other factors equal).

The plan is to set the cruise control to 60 on day 1, 70 on day 2, and 80 on day 3. I'll use the same set speed for both the trip to work and home each day.

The particulars of my commute are as follows:

- 27 miles
- Home is 220 feet elevation, work is sea level
- The freeway (CA-85) was constructed to minimize noise to the surrounding neighborhoods, so it's in a sort of trench. It dips down when going under an overpass and rises back up on the otherside (overpass is flat to those crossing it). In other words, lots of ups and downs.

The car had 250 total miles before this test began. Tires are at 32PSI (I'll pump them up to ~40 after this test is complete).

Here are the results for today (60 miles per hour):

Home -> Work

Trip Mileage: 51.4 MPG
Set Speed: 60 miles per hour
Temp: 56 (start), 55 (end)
SoC: 63% (start), 100% (end)
Time: 43 minutes
Notes: At least one bar of regen was showing for the first 6 miles, except when climbing. There was a 5 mile stretch of stop-n-go traffic.

Work -> Home

Trip Mileage: 52.0 MPG
Set Speed: 60 miles per hour
Temp: 64 (start), 55 (end)
SoC: 75% (start), 88% (end)
Time: 34 minutes
Notes: Full speed the whole time (light traffic). At least one bar of regen was showing for the first 20 miles, and the car went into fuel cutoff mode much less than my ride in, although this didn't seem to adversly affect my mileage. I also saw the instant MPG gauge hovering just below 100 MPG for extended (20-30 sec) periods, with the next to last block switching on and off. I've never seen this condition before; normally the guage is very dynamic between 65 and 100, meaning that when it's in this range it's usually on the way up or down rapidly. When it's on the way up, it usually pegs and goes into ICE-off mode.

BTW, now that I am more tuned to the car, I can actually feel the slight vibration difference when the ICE comes back on after being in fuel cutoff mode. It often happens when I'm not looking at the instant MPG gauge and the vibration change alerts me that something has changed. It always causes me to glance at the instant gauge, and sure enough, it's falling off after being pegged. This gives me more confidence that the valves really are sealed when the gauge is pegged. I don't feel it going INTO fuel cutoff mode, however.

Tomorrow, 70 miles per hour.

haha nice nice! i predict your mileage will fall to mid 40's and with 80 miles per hour you'll be around the 30's.

wow and your civic hasn't even broken in yet... go honda!

2003 toyota prius, 55 mpg lifetime starting.

Sounds like a good setup- I recommend a few round trips at each speed. One thing you'll find is "your mileage may vary" even with seemingly identical temps, traffic conditions, etc, so it may be worthwhile to avergage a little at each speed increment.

Also don't forget that your car is in its breakin period- soon mpg will go up independently of any driving technique, and it will be difficult to calibrate that back out since you're the single test point on this vehicle right now. So running a control is difficult for you at the moment. The HAH and HCH (I think) have generally seen significant mpg kicks at 1200-1500 miles and again around 3k.

I am very interested in this test.

I use cruise control every day on my (17.2 mile one-way) commute, 99% freeway.

I also have a fairly flat commute with a few ups and downs for freeway interchanges and such.

I got 64.7 MPG this morning.
It is hard to imagine it could get much better by taking it out of cruise control.
My gut tells me that whatever gravity takes away going uphill it gives back going downhill.
Plus it is a lot more hassle and mental energy to do all that stuff.
I'm happy with my lifetime average of 60.0 MPG on cruise control.

I'm not saying all the lean burn or pulse and glide techniques don't work; I'm just saying I'm getting good enough MPG on cruise control.
Just another opinion.
YMMV.

Also my MPG varies 3 MPG or so for no apparent reason from day to day.
Could be temp, humidity, or wind or the phase of the moon.

True, and it's also going to get colder soon. This test is just a snapshot, but interesting nonetheless. I'll probably repeat the whole test again next spring when the temps are about the same as they are now.

Another interesting thing I've noticed about the cruise control is that it allows enough regen to keep the battery at 100%. I've seen a bar of regen even on a slight downhill. If I were controlling the throttle, I could cancel that out and probably do better, but at some point you have to pay for the assist you use during acceleration (it's hard to accelerate w/o assist unless you are very patient).

Driving at 60 miles per hour is a strange experience on California freeways. I was driving in the middle lane and I felt like a log stuck in a river; all of the other cars were flowing around me on both sides

Stay to the rightmost lane.
You and everyone else will be safer.

The problem with that is that it's hard to maintain a constant speed with other cars constantly merging on/off that lane.

Nice experiment, NASAgineer!
Please don't do what gonavy says, I don't want to wait through several trips at each speed to see the results for 70 and 80.
Kenny's results at 50mph with cruise control are interesting to me, because I can arrange for much of my driving to be at 50.
--Walter
P.S. I'm afraid the first numbers my eyes were drawn to were the temps, 56, 55, 64, 55
Here it's 30F and falling with snow

Then you probably don't want to hear that it's been 84 degrees these past few days in San Diego, and cloudless.