As a brank new HCH II owner, I've been trying many of the great pieces of advice by you hypermilers out there.

Would you be willing to weigh in on what you would consider the greatest benefits to FE (fuel economy) by posting your ranking of what the greatest killers of FE are? If you could give a rationale as to why you've placed them in the order you listed, it would be a great debate to start.

Listed alphabetically

1 - Air Conditioner on

2 - Cruise control use

3 - Full tank vs. half tank of gas

4 - Hills

5 - Jack Rabbit starts

6 - Low Tire pressure

7 - Stop and Go driving

8 - Weather (temp and rain)

9 - Weight in trunk

10 -Wind Resistance

(if you have any others I've missed, please feel free to add them to the list)

 

hi

good post. i will take these under advisement. I am going to start hypermiling.

 

Here's my thoughts on the matter

1 - Air Conditioner on
(noticed this one real quickly - turning it off on the morning commute with the temp isn't as high really saves on the FE. Its too hot to do it on the way home though)

2 - Hills
(going uphill really drops the FE fast. I'd stay away from hills as much as possible.)

3 - Jack Rabbit starts
(much better to start slowly. If you can pick up speed going downhill thats even more of a plus.)

4 -Wind Resistance
(once I get above 65 I see a pretty big drop in the FE)

5 - Weather (temp and rain)
(put it at 5 just because it forces me to use the AC when it gets hot. Haven't had the car long enough to notice a difference in the winter)

6 - Weight in trunk
(just seems to make sense that less weight makes it easier to get higher FE)

7 - Stop and Go driving
(it messes me up when I can't get my HCH to go into auto-stop all the time. This especially happens when the stop and go traffic is going uphill. That's the worst!!)

8 - Cruise control use
(put this a little lower because it seems like I can regulate almost as good as the cruise. Probably would help on a long trip so I don't have to be so focused.)

9 - Low Tire pressure
(This might be a bit low for this one, but it seems like there's a lot of discrepancy regarding the issue.)

10 - Full tank vs. half tank of gas
(don't know enough about this one yet. I'll have to research it a little.)

 

Some will argue that cruise will help MPG. Perhaps it doesn't hurt much on the flat but cruise and hills don't mix IMO.

Hills really are not a problem because for the most part whatever extra gas you put into climbing you get back on the downhill side, especially if you FAS it.

I guess you have excessive speed covered by wind resistance. Speed kills mileage faster than anything.

 

Hi Jeffrey,

There is a vehicle specific componet to these. Although many are to a greater or lessor mode shared, there is one biggie for the Prius pilot.
Stop and go taffic usually means lower speeds putting the Prius in a better fuel efficiency range. The average EPA speed for City is about 20 mph and both models of Prius get higher MPG in City operation compared to the Highway. The large Prius MG2 and battery pack handles regenerative braking and electric only modes at slow speed, City driving. This is true as long as the speeds are 38 mph and below, a 4 mph guard band away from 42 mph.

Due to the transition speed of 42 mph, Prius drivers should avoid 39-50 mph. This is unique to the Prius and has to do with a transition between two types of control laws. This also means that a Prius going at highway speeds is OK but they need to stay there as long as possible. My NHW11 Prius is rated at 45 MPG in the EPA Highway test which has a speed of 48 mph. But at 51-65 MPH, I regularly get 55 MPG.

Both vehicles begin to suffer significant mileage hits starting at 65 mph air speed. Head and side winds require a lower highway speed and tail winds allow a little higher.

Bob Wilson

 

This is a good list - jeffreykime.

Let's rank them starting with those that hurt your fuel economy the worst:

The two most important

• 5 - Jack Rabbit starts (Stop-and-Go) If you look at the instant mpg bar (those of you that have one), fuel economy plunges. If you intend to get a lot of miles on a tank, you will accelerate gently. Two things that hurt your trip mpg quickly is the catalytic converter warming up (can't do a lot about that) and moderating accelerations. This is true of my 2000 Insight and 1974 Opel Manta, so it may be a good generalism for most vehicles: Your fuel economy doing Fast and Furious type of stop-and-go driving at 40mph will be as bad as a steady cruise at 80 mph on the freeway. Conservating momentum is the most important thing to improving your fuel economy
• 10 -Wind Resistance (Speed) If you read the little message on the Shell Gas pump, you may have noticed "highway speeding can reduce your fuel economy by as much as 33%". Ballpark this would be the difference between doing 80 and doing 55 or 60. Wind resistance goes up geometrically and become a bigger factor than weight.

Also Important

• 4 - Hills - It simply takes more energy to go both forward and up. One way of cutting your losses is gradually increase your speed as you approach the hill. Depending on how big the hill is, try not to give it a lot of gas and allow your speed to drop some.
• 8 - Weather (temp and rain) If it's severe, this hurts maybe more than anything else. A severely iced road makes driving over 20mph dangerous. High wind and rains also make a severe impact.
• 1 - Air Conditioner on. Even with afternoon highs near 100F, it's possible to use the A/C very lightly if you are not dressed in a shirt-and-tie. Use a shelter (garage or tree) whenever you can. Toggle the A/C on when braking, coasting, stoping - fan only otherwise
  
  

Generally not that Critical

• 2 - Cruise control use. Actually I'm not that sure, but my cruise control experience is not positive. It works better on large and performance vehicles and not so well on subcompacts. Fuel economy will be hurt is there are a lot of hills.
• 3 - Full tank vs. half tank of gas
• 6 - Low Tire pressure. Might be significant if pressure is really low.
• 9 - Weight in trunk At most this is a couple of hundred of pounds. Wind reistance is much more significant.

 

I think the takeaway on CC is that it will help FE for 99% of the normal drivers out there who will give no heed to other tips/have no more than a casual interest in using less fuel. It's about the most 'extreme' thing they are willing to do, based on observing my wife, parents, in-laws.

So telling people to use CC is positive for almost everyone. NOT for many of us here, though. If nothing else, it puts an upper limit (sort of) on their speed for most of a trip.

FWIW, I personally use CC religiously to ensure I stay at 60- the added benefit of DWL beyond that is minimal, and outweighed by the added concentration/effort reuired for me. I drove with the load for about 9 months before going back to CC, and my tank records show the lack of) difference. For me, the biggest boost was regularly driving as though my brakes were a last resort means of slowingthe car.

 

Probably already mentioned
1)Short trips-under 3 miles in the summer,a bit farther in the winter.It takes the Prius about 2.5-3 miles in 90 degree weather to get hot enough for it to go all electric and shut the ice down.We do lots of short trips.To its credit the Prius will still get 38-40 mph on a 2 mile trip with a cold(overnight) engine.The same trip, if extended to 4 miles will become a 50+mpg trip because I can get it to go all electric for 80% of the last mile.
Thanks,Charlie

 

This is why I'm looking at a modified cruise control. Having the driver in the loop leads to inconsistent results and worse. I've ordered a TI microcontroller that should be able to handle the Prius CC resistor network to implement some experimental cruise control laws:

1) 0-"n" mph range based upon 'load' to let the car seek minimum fuel consumption
2) neutral glide to handle coasting
3) nibble down to 38 or up to 51 if speed is set in 39-50 mph range (Prius specific)

This microcontroller has the ability to record to flash and comes with a USB programming interface. My modification uses the microcontroller interfaces to sense and operate the CC resistor network. In the Prius, the CC takes digital up/down inputs and for safety, can easily be disabled.

Bob Wilson

 

Here's my take, some have already touched on these.
My opinion is based as a hypermiler, not 99.999999 of other drivers:

1 - Air Conditioner on
Isn't too bad of FE hit if pulsed. That is if only on while either slowing down or going downhill. A big taboo to drag the compressor while accelerating or climbing a hill. This is where even the "Auto" feature isn't very good.
When the family is along I pulse when neccessary, even in 97 degree 98% humidity. Still takes a hit but not nearly as bad as just "on" or "Auto".
(I'm not sure how the new hybrid-electric compressor behaves though.)
2 - Cruise control use
Almost useless for an extreme hypermiler. The only use I find is briefly to keep the car going while I remove my Right shoe.
WAY too much exessive battery use in hilly regions.
3 - Full tank vs. half tank of gas
More accurate measure is from full to empty. I couldn't go the distance on half a tank.
4 - Hills
Not too bad a hit if one knows how to handle them. (DWL) The exception is finding yourself slow/stopped at the base of a hill or worse gridlock stop-n-go traffic on a steep mile(s) uphill.
10 -Wind Resistance
This can usually be brought into control by adjusting speed or take different routes.
(In a head/x-wind better to take it easy a tree-lined highway rather than naked out on a fast-paced freeway)
11 - Other careless driver who use your car(Not mentioned)
I keep her car gassed up, clean and as convenient as possible so she leaves mine alone!