I find in practice that accelerating very slowly vs. rapidly makes minimal difference so long as I can preserve my momentum once I'm up to speed. It will require the same amount of energy to accelerate the mass of the car to a given speed no matter what, the differential efficiency of the engine at the respective RPMs is the issue, and on a CVT I find that it's about the same across a fairly broad range of accelerating styles.


I disagree. Slow steady acceleration uses the ICE almost exclusively. That means that any momentum that you gain is by burning fuel. On the other hand if you accelerate quickly the electric motor comes into play....therefore less energy is coming from the ICE...therefore lower fuel consumption.

There may not be a lot of difference in FE but it is there, and...at least you're driving at a more normal rate to surrounding traffic

[quote=worthywads]What are you some kind of apologist for the SUV folks.

No...a black hole for power from others....

Hills are by far the worst thing. They should be number one. You don't even come close to making up the gas mileage lost going up a hill by going down the other side. If you live in a hilly area, you can pretty much kiss your fuel economy good-bye. A person can blast the AC in a flat area and still outperform city driving with hills. Hills aren't quite as bad in highway driving maybe, but they still are bad.

Regarding the whole speeding up thing, I guess I fall into the camp that believes in electric assist for acceleration. I find that I almost always have way too much battery charge, so there's no need to fear using it for something. All your regenning doesn't accomplish much if your battery charge is maxed out and can't hold anymore. So, I say, use that power while you can. By far the most important thing is to maintain speed once you have it, but even if there's another light up ahead I just give it a quick burst of power to get me rolling and then coast on in to a stop. Let me add this is with a CVT (sadly). With a manual there may be some advantage to slow acceleration as you have more control over the gear, etc.

Now, in a normal car you need to accelerate slowly. I sometimes find myself making this mistake since I am not used to do doing so.

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.

Below I've listed my rankings for my Prius II prior to your alphabetic list:

Listed alphabetically


#1 - Short trips - By a HUGE margin
Possibly as much as a 20-30% loss in FE

( 2 ) Highspeed driving at above 65 mph.
This can reduce your FE by as much as 15-20% although the new Camry Hybrid seems to defy the laws of physics ( or Toyota adjusted the testing ) because it seems that there is little or no loss in FE at 70 mph vis-a-vis the EPA Highway tests ( supposedly done at about 48 mph ).

( 3 ) 8 - Weather (temp and rain)
I just did a 50 mi run in a rainstorm with heavy runoff over the road and lost 15% over dry road driving. This is the worst condition I've driven in yet.


( 4 ) 10 -Wind Resistance
Driving into a stiff headwind is a killer. Think riding a bike into a wind. I'd estimate a 10% loss in FE.

( 5 ) Cold weather driving
This will reduce every vehicle's FE by about 10%

( 7 ) 1 - Air Conditioner on

( 11 ) 2 - Cruise control use
Minor effect if any

( ? ) 3 - Full tank vs. half tank of gas
There is no effect as far as I can tell.

( 6 ) 4 - Hills
Although for every uphill there normally is a downhill thus it should even out

( 8 ) 5 - Jack Rabbit starts
This is usually not a concern at all in the Prius unless it's one after another after another.

( 10 ) 6 - Low Tire pressure

( ? ) 7 - Stop and Go driving
This is one area where the Prius shines unless it's between multiple stop signs.

( 6 ) 9 - Weight in trunk



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

You have to have the giant Ham antennas, no sense driving otherwise. If you can't take your radio with you, no sense leaving the shack.

73,

N5KF
06 HCH

Great List.

However, for those of us who drive north of the 45th parallel (especially in the prairies) can expect cold weather driving to be a 40% (often more) hit on fuel economy - thus making it the #1 FE Killer.

Yes, I am talking about 4-6 months worth of -4F to -40F in persistently lowsy road conditions.

Cheers;

MSantos