Fuel Efficient Driving

[Orion21]

I was wondering about both the most fuel efficient way to accelerate. Is it better to accelerate slowly and keep rpms low or to accelerate quickly with higher rpms?

I thought it was slow acceleration but after looking about it seems that accelerating quicker with more pressure on the accelerator pedal might be better between roughly 2k-4k rpm for most cars before changing to a higher gear.

Also when maintaining a constant speed is it best to keep rpms as low as possible (i.e. say 1k to 1.5k rpms) or is it better to keep them between a certain rev range which is higher for fuel efficiency?

 

[Orion21]

I take it by engine under load you mean either at low revs where it is sluggish at accelerating or if climbing a hill in a high gear?

I had also read stuff about accelerating hard (not sure if they meant with pedal fully or almost fully depressed) to get up to speed quickly and then changing to a higher gear when cruising at constant speed. From reading about it they seemed to be suggesting that overall this was more efficient. Sounds like what Hiijinx mentioned.

Of course this all assumes no obstructions causing you to brake etc as forward planning is better. But I'm specifically wondering about most efficient acceleration and cruising gear.

I'd always thought low revs and slow acceleration was best and when I'm driving sensibly and trying to be fuel efficient I tend to keep revs lows, gear high and throttle pressed gently for acceleration. Now I'm wondering if I was going about that wrong and should have slightly higher revs before gear changing as well as being a bit heavier on the throttle.

 

[Orion21]

I know about predicting conditions etc being good for fuel efficient driving.

What I am curious about is specifically the most fuel efficient way to get to speed assuming there is nothing that is going to cause you to brake and lose that speed again which would obviously be wasteful.

From looking at replies here and using google it now seems that fast acceleration possibly with gas pedal pushed almost all the way down is best for fuel efficient acceleration and then when you get to speed desired change to highest suitable gear to maintain that speed which is likely 5th but could be 4th if on a hill.

Also came across fuel consumption curves etc such as http://physics.stackexchange.com/qu...acceleration-minimize-a-cars-fuel-consumption but I'm not entirely sure I understand what it shows.