Fuel efficient driving scenarios....?

[rlaggren]

Here's a couple sites I ran across recently. In true scientific fashion (or just to repackage "their" presentation) they have made a basic concept totally complex, to the point that I'm not sure whether they have something to say or not. They relate all this stuff to the readouts on a hybrid, but I'd _think_ it should apply to any vehicle.

Near as I can understand, they're saying to speed up then coast down, averaging at the speed you want to travel. The only reason I can see that helping is if the torque curve if the engine doens't "fit" the speed you want to cruse at - but that still doesn't sound like a good reason not to maintain a steady speed.

Anybody want to wade throught this?

http://www.gassavers.org/
http://www.cleanmpg.com/

Rufus

[kassim503]

I doubt that technique works, it may work for the prius or a hybrid chassis. I think if I was driving down a road id get it to whatever speed I need to be and try to do it so I dont have to overthrottle and then ease off. Thats why cruise control helps fuel economy so much.

If I understand correctly, in a hybrid chassis it uses the gas motor on accleration, and at speeds over 30 or something. It might pay off to speed up using gas, and let the electric motor try to power you as you slow down. Im not sure when the electric motor is engaged or not. To me thats just a bunch of expensive hooey for only 5 mpg more.

[glenlloyd]

Personally I'd get very tired of that speed up / coast technique pretty fast. I would imagine that it would annoy a lot of people on two lane roads as well!

That said, I will admit that in the Golf I sometimes use a downhill to build up speed so that I don't lose a lot of momentum when going up the otherside. Since the Golf only has between 52 and 54 hp it's a bit of a struggle sometimes, especially if there's a headwind. Otherwise I like a steady pace.

steve a

[Carimbo]

Often when I get stuck behind a Prius I can't figure out what their driving method is. This may help explain?

My method is to attempt to stay close to the speed limit (if conditions allow) and drive SMOOTHLY, anticipate hills, curves, etc. Change lanes when there is plenty of space, keep out of others' way, use turn signal w/ plenty of advance warning. NEVER telephone, don't even like to talk much while driving, I seem to be one of those who can only seem to concentrate on one thing at a time. Driving SMOOTHLY can often be challenging and gives me a certain satisfaction when I can pull it off.

[rlaggren]

Driving smoothly is the way I've always heard is best. Amazing how much easier it is to remember to do it with an "under powered" car or a truck; put me in a "sporty" car and I just mash that go-peddle without thinking.

But Steve's Golf note reminds me of the 84 Honda Accord and the 86(?) Tercel I drove. Those cars I had to downshift to keep 55mph up most long hills. Now I think about it, it would have been better to build up speed on the downslope to use on the next upslope to keep from revving the engine in a lower gear - get the same distance (down & up) with fewer engine revs. So that way looks like it makes sense to not try to keep a constant speed.

Hmmm. But I really don't get shy changing speeds would work otherwise. I think I read that the pro drivers the manufacturers use to record their mileage claims use the accel/coast system so there must be _something_ to it.

Rufus