Fuel Economy

On my way to the golf course I drive through rolling hills, up and down for a mile or so from hollow to hollow. Am I better off gently coasting downhill maintaining a fairly constant speed up and down, or should I gun it downhill and coast up the hills?

Too many unknowns to make a meaningful answer.
Try it both ways and see.

Gun it downhill and coast up the hills. If the cops don’t shoot you, the drivers behind you will!

Widely varying your speed on a rolling road is the best way I know of the cause road rage. Whether it saves gas or not, it’s unsafe driving. Please refrain from doing it.

Most of us want to maximize our gas mileage.
However, many of the possible methods for maximizing gas mileage will result in (pick one or both):

Putting yourself and other motorists in danger
Inducing road rage in those who have to share the road with you

Unless you are lucky enough to drive on roads that are free of other vehicles, your best bets for maximizing your gas mileage are:

Maintain the car flawlessly, including use of the oil viscosity specified by the car’s manufacturer.
Make believe that there is a raw egg between your foot and the pedals (in other words, only use very gentle applications of the gas pedal and the brake pedal)
Make sure that your tires are inflated to at least the PSI specified by the car manufacturer, or inflate them to…perhaps…3 psi over the car mfr’s recommendation.
Take excess weight/cargo out of the trunk/cargo area
Don’t tailgate (if you don’t understand this point, admit it and I will explain it for you)
Don’t “warm up” the engine for more than…perhaps 30 seconds or so.
Don’t use drive-up windows at banks and fast-food joints (Your butt will benefit as much as your MPGs!)
Remove the roof rack if you have one
Use the same octane gas specified by the car’s mfr
Keep the wheels aligned properly
Don’t drive faster than 60 mph

Even if you can only do 6 or 7 of the above items, you will be doing more than most folks in terms of maximizing gas mileage, but the one thing to do without fail is to maintain the car flawlessly. And, in case you are not aware of it, car maintenance includes A LOT more than just changing the oil.

To answer your question, accelerating gently downhill and easing off a little uphill will produce the best mileage. A vacuum gauge will give you a visual indication of how you are doing…

Hold a steady throttle, let the car pick up speed going downhill and bleed a little off going up hill. This should not annoy other drivers either as most people who are not on cruise control do this naturally. Do not use cruise control in this terrain.

Keith’s method is how I do it unless it’s some 7% downhill grade in CO and in that case I ride the brakes a bit now and then to keep the speed from gettng too excessive.

Oh yea, my method works better in Tennessee than it does in Colorado.

Obey the speed limit., drive safely, let the mileage take care of itself. If you have to control your speed over long down hills, do it in a way that reflects the advice of your owners manual.

When you eventually own a car with an instant readout fuel mileage computer, you will see that accelerating gently at any time is the way to do it. As Caddyman correctly said, accelerate gently downhill and let your speed ease off while going uphill. You can do this when there is no traffic behind to be annoyed. You will not, I predict, become wealthy if you are not so already, from the gas money saved.

Drive gently and maintain your speed. Keep enough distance between you and the car in front of you that you can react to his moves without jamming on the brakes or making emergency maneuvers. Don’t do anything quickly. If you see a red light ahead, slow early and hope that you don’t have to stop when the light changes. No jackrabbit starts. Don’t go over the speed limit (well, not much - let’s be practical). Cars are geared to provide good mileage at the speed limits. I don’t have to exceed 2000 RPM in 5th gear up to 65 MPH, and can cruise at 55 in 5th gear, too.

Just about everything “jt” outlines pretty much conforms to safe driving techniques. Going beyond that which so called hyper milers use to extract that final few miles per gallon just isn’t worth the extra risk to themselves and those they share the road with.

@oldsport, when I’m hauling a heavy load, or towing, I might let the vehicle slow down slightly while going uphill, and then accelerate going downhill, but with most cars, under normal circumstances, it doesn’t take that much fuel to maintain speed while going uphill. What uses the most fuel is accelerating while going uphill. If I were you, I would just set the cruise control and not worry about it.

With respect, Keith, I was taught to maintain a constant speed. I’d argue that most drivers try to do so. Slowing going uphills and gaining speed going down hills drives me nuts (if i’m behind you). I’m betting others feel the same way I do.

People, care to cast a vote?

I let the car coast (in gear!) going down hill, to get as much momentum as I can without reaching a speed that would get me a ticket, and I try to use the throttle gently on the uphill parts so as not to slow too much. I don’t maintain a perfectly constant speed, but keep it steady enough and sufficiently fast so as not to drive the guy behind me nuts. NEVER coast in neutral!

Gas going up, coast going down; that’s how Ido it.

Without a doubt, maintaining a constant speed is paramount in safe driving. This always takes a president over maxing mileage as driving isn’t a game. Constant speed is essential in maintaining a cushion which allows you the reaction time needed for unforeseen maneuvers. More people should use their cruise controls more in areas that are appropriate.

Unfortunately, we are a highway filled with control freaks who feel it necessary to drive cars like they are rushing through line trying to get a ticket to a rock concert. The cemetery is filled with one time drivers who thought they had everything under control.

It is the only activity where you put your life in the hands of others who put their life in yours on a regular basis. That is an awesome responsibility that many drivers take for granted. Any discussion about anything having to do with driving, maxing mileage or otherwise, that does not include safe driving techniques is BS and does more to contribute to the chaos on our highways then solve it.

Maybe we can all agree that the goal should be minimizing the TOTAL cost of travel on public roads.
Optimizing should be in this order of priority:

  1. Minimize cost of damage to people and property. Part of this is minimizing influence on other drivers: don’t be a road hazard.
  2. Minimize wear and tear on one’s own vehicle. Drive gently and keep up maintenance and repairs.
  3. Minimize fuel consumption. Again drive gently, moderate speed, combine trips etc.

Cannot agree. The goal should be maximizing safety. Cost minimization should come second.
Maximizing safety includes maintaining a steady speed.
Minimizing cost can be accomplished by accelerating moderately, planning ahead, and keeping the vehicle in shape…which, I aould argue, all complement safety.

I think we just disagree on terminology.
What you call maximizing safety I call minimizing cost of damage, ie. accident avoidance.
Maintaining a steady speed is one way to minimize influence on other drivers: by being predictable and not forcing them to guess what you’re going to do next.