I always think of it this way. If you ever feel your engine start to bog down a little its running richer, so there is a little gas that is not getting used to its fullest potential. That is not a fact. That is how I justify my actions. I get my best mpg on hills because I don't use my cruise control. I usually feather the throttle the entire time. I keep the engine running lean as I can while still slightly accelerating downhill, so I can slightly decelerate going up the next hill. I usually maintain speed at the base of a hill and then the more I get up the more I'll let off to keep the engine running lean as the rpm's drop. By the time I get to the top my gas petal is at or around its highest point in the cycle and I repeat. Works good for me!
You just about perfectly described the "Driving with load" technique, and it is VERY effective on hills.
Originally Posted by Quadrunner
I never understood the point of coasting in neutral unless maybe its on your final hill or two before a stop. Your engine is still running and you still have drivetrain friction since the drive wheels are connected to the transmission all the time. It seems like your paying for a slight increase in mpg with drivetrain stress from the extra shifting from neutral to high gear. I guess I like my car too much. There is also the consideration here that the more your speed fluctuates, the more you will lose to air drag at the bottom of the hill. If you feel your car begin to near terminal velocity in Georgia overdrive, its a good indication you could be doing a little better. Just my humble opinion. I don't have the computers to back it up, and my newest cars have historically been about 15 years old.
Vehicles with electronic fuel injection will shut down the injectors (Fuel Cut) and engine brake if left in gear. This is fine on steep hills, but on more gradual hills, you can either idle the engine and coast in Neutral, or leave it in drive and hold your foot on the throttle. Personally, I use all of the techniques you describe (Driving With Load, Neutral Glide, and Fuel Cut) depending on my speed, incline of hill, traffic, and whether I intend to speed up, or slow down.
Thanks for the input. Recently I have been trying the exact technique you described, being gentle, and not accelerating hard but progressively. I try to keep the turbo just on boost, not so much that it's using too much fuel, but just enough to pull me up the hill. I still loose speed, that's the only thing as it's obviously a small car and some of these hills are pretty big, the only way to avoid loosing speed is to apply maximum throttle, but then that's a huge waste of fuel.
I tried that, and the hills are often too long and I gradually loose too much speed. Once I reach about 45 Mph, the gsi (gear shift indicator) tells me to change into 4th. So now I'm changing into 4th and feathering the throttle more using higher revs instead. Not sure if it's any more or any less efficient yet.