Achieving High MPG on Freeway Trips

Billy · 06-23-2009, 12:59 AM

Several people have asked me how I got 107.6 mpg driving from WA state out to the midwest. Here is the answer; not intended as boasting, just informational. Besides, the emphasis is on the Honda Insight, not me personally.

In July of 2007 I departed Tri-Cities, WA (Pasco) heading for Wadsworth, IL to visit Wayne Gerdes just prior to Hybridfest in Madison, WI. I planned the trip carefully and was hoping to get 110 mpg (if I had some tailwinds, I would have easily done 110+)

First, this was my 3rd Insight that I'd purchased new, and I had 160,000 total miles on Insights. And I'd been "hypermiling" as a hobby since 1979. Therefore, I had a pretty good feel for the car and knew lots of ways to prepare the car and use efficient driving techniques.

Remember, this is summertime travel and warm temps always help the Insight mpg by a substantial amount. I removed the passenger seat (33 lbs), this car had NO A/C, tires were inflated to 57 lbs, I was equipped with a Scangauge and GPS.

The route took me south to Hermiston, OR where I picked up I-84. After a long steep climb up the Blue Mtns from Pendleton to Meacham, it was downhill to LaGrande. I went through Baker, Ontario, Boise, Twin Falls, Burley, Tremonton, Ogden; then went East on I-80. There is a long climb to 6600 ft up to Evanston, WY. Farther east is Laramie, one of my favorite towns. Just east of Laramie there is an 8700' pass, then it's downhill to Cheyenne and way beyond, into Nebraska. I had the engine shut off (FAS) for over 32 miles straight, then it was off again for about 30 of the next 35 miles. I continued on I-80 through NE, IA, IL and arrived at Wayne's house showing 107.6 mpg.

On this trip the key was to NOT be in too much of a hurry. I drove about 55 mph on flat ground, and much slower ascending hills. Using no assist on hills is a great method of saving fuel. Then you can coast down the other side with the engine off, and still having a full battery charge. Lane positioning is also important. Drive on the crown rather than down in a groove. And drive on concrete instead of asphalt, if you have a choice. Also, I drove the whole trip with stocking feet; maximum sensitivity to the gas pedal is vital.

So basically it's just this: put lots of air in the tires, slow down, stay OUT of assist mode, coast (engine off) as much as possible, and try to remain in LEAN BURN when you can. Keep the vehicle light, use synthetic oil, turn the A/C off.

bryankwalton · 06-23-2009, 09:29 AM

Quote:

Originally Posted by Billy

I had the engine shut off (FAS) for over 32 miles straight, then it was off again for about 30 of the next 35 miles.

Hi Billy, thanks for the writeup. Once question if you were in FAS for 32 straight miles, I'm assuming that you were going downhill. How did you avoid using the brakes during those 32 miles? Did the car get to a certain speed and not get any faster? Were there no turns that required slowing down? The reason I ask is that I know that if I'm in FAS mode, I can't use the brakes for very long or I lose them.

Thanks,
Bryan

02insight · 06-23-2009, 11:55 AM

I've tried all your tips, but the highest I can maintain on a flat stretch of highway going 50mph is 85-90mpg. This is during lean burn, no assist, full battery charge, no wind. If I let off the throttle the slightest more, the mpg will go up to 110, but the car will start to slowly decelerate '.

This seems normal ? Or maybe its the fact that my insight is still completely stock. So I guess the removal of a seat, ac components, side mirrors etc... would help get me over the 100mpg barrier.

ikhoudvanu199 · 06-23-2009, 12:20 PM

Quote:

Originally Posted by 02insight

I've tried all your tips, but the highest I can maintain on a flat stretch of highway going 50mph is 85-90mpg. This is during lean burn, no assist, full battery charge, no wind. If I let off the throttle the slightest more, the mpg will go up to 110, but the car will start to slowly decelerate '.

This seems normal ? Or maybe its the fact that my insight is still completely stock. So I guess the removal of a seat, ac components, side mirrors etc... would help get me over the 100mpg barrier.

those numbers seem perfectly correct given your circumstances, nothing to worry about

3-Wheeler · 06-23-2009, 01:34 PM

Hi Billy,

Since I was one of those people asking how Billy got such high mileage, it's a very interesting read. Thanks.

You mentioned that your car does not have A/C. My 2000 does and would be very interested to find out if there is an easy way to disable it? It seems that rerouting the serpentine belt to bypass the compressor is always one of the bottle necks to performing such an operation. And then getting a shorter belt to fit in the available space. Sometimes bulges other objects keep this from happening. I have not looked closely at this on the Insight however.

Has anyone effectively disabled an A/C Insight?

Thanks, Jim.

Billy · 06-23-2009, 02:20 PM

Hi Bryan; the 32 miles of FAS I mentioned, is one of the longest interstate freeway downhills in the nation. There are a few parts steep enough where I had to use brakes. By the way, the brakes never "go away", they just loose hydraulic assist after a few pedal pushes. Then you just have to push real hard and they work fine. (takes some getting use to). Anyway, I absolutely love these downhill sections. It's a great feeling to be cruising downhill with the engine off, and seeing how long you can "milk it" to get over the hump to the next downhill section. After awhile, you get the ability to look far ahead and ESTIMATE the angle of slope and judge whether or not you can coast.

Billy · 06-23-2009, 02:31 PM

Hi 3 Wheeler; I don't think the issue is "disabling the A/C". Rather, I specifically ordered this Insight without A/C because of the 37 lb weight savings. But frankly, the increase in MPG over my other Insights WITH A/C is between miniscule and non-measurable. Perhaps the very slight drag of the compressor pulley (even when compressor is off) is a factor, but not much. Therefore, one could remove the A/C condenser, compressor, evaporator, hoses, etc. to save weight, but it would reduce the resale value of the car.......

For O2; 85-90 mpg on flat ground as you describe is excellent. When you add to that lots of coasting, you can see where 100+ is possible. Also, varying your speed (mph) to carefully suit the current conditions is good for another 3-4 mpg. For example, slowing to 47 mph for a short time in order to keep the meter above 125 mpg would help. Then driving 68 mph on a VERY slight downgrade (engine on) would make up some time. Bottom line is, do whatever you can to expand your lean burn envelope, then coast when possible....

red1dr · 06-24-2009, 07:03 AM

Quote:

Originally Posted by bryankwalton

One question if you were in FAS for 32 straight miles, I'm assuming that you were going downhill. How did you avoid using the brakes during those 32 miles? Did the car get to a certain speed and not get any faster? Were there no turns that required slowing down? The reason I ask is that I know that if I'm in FAS mode, I can't use the brakes for very long or I lose them.
Thanks,
Bryan

There's another strategy rather than using the brakes. If the hill is so steep that you pick up speed, simply leave the engine on and the car in gear, and take your foot off the gas pedal. Engine braking and regen will help to slow you down. You will burn zero fuel thanks to fuel cut (assuming the rpm is >1100) and will also regen the battery (even if you have been staying out of assist, a little regen helps replace the losses due to the EPS and other systems). And the spinning engine will maintain your brake boost vac.

For steeper downhills, try using a lower gear or lightly pressing on the brake pedal to add in more regen braking. Or if you have MIMA you can use the joystick to add regen (assuming the battery SOC is not maxed).

I try to avoid going faster than 55mph on downhills unless the battery is maxed: rather than waste energy to the increased air drag of higher speeds it helps to capture at least some of it by regen-ing the battery. I use this method on steep downhills on secondary roads as well, to avoid exceeding the speed limit.

I try to categorize downgrades as:
(a) not steep enough to coast down
(b) steep enough to coast but not so steep that speed will increase
(c) steeper, requiring the above method to hold speed down
(d) really steep, downshifting and/ or friction brakes needed if battery is full

bryankwalton · 06-24-2009, 07:10 AM

Quote:

Originally Posted by Billy

Hi Bryan; the 32 miles of FAS I mentioned, is one of the longest interstate freeway downhills in the nation. There are a few parts steep enough where I had to use brakes.

Thanks for the reply. That is what I suspected. But, having never driven that stretch of road before, I was figuring that coming down out of the Rockies would have to be very steep. Guess not.

Cheers,
Bryan

Cobb · 06-24-2009, 11:59 AM

SO, the insight 2 owners should consider using the sport mode and a gear that does not dip into assist for the same effect? I find using a gear once to avoid the blue screen or assist lowered my fuel economy.

Quote:

Originally Posted by Billy

On this trip the key was to NOT be in too much of a hurry. I drove about 55 mph on flat ground, and much slower ascending hills. Using no assist on hills is a great method of saving fuel. Then you can coast down the other side with the engine off, and still having a full battery charge.