Is there any point to P&G in a diesel?

[bluetwo]

I say any time you can coast regardless of the grade it's worth it to pulse a bit or get up a little extra momentum so you can get the most out of the coast or glide. I hate the term pulse and glide because it just sound deceptive, as if I'm not just accelerating then coasting. But whatever, glide whenever you can is my advise but don't get too carried away with trying to pulse and glade all the time.

[JacobAziza]

Ah, yes, I do always coast when possible with just the slightest down grade. It changes everything when you have gravity on your side.

When I first posted this, I was thinking about perfectly level ground.

[bluetwo]

Right.... and I'm not sure if downhill was meant but the main thing I think people should take from it is unless you're in a car with Hybrid Synergy Drive you shouldn't try to pulse and glide all the time like it's going to give you much better mileage. It works for those cars because the engine can autostop while the car is still at decent speed.

[dcb]

I don't follow. One can stop the engine anytime without owning a synergy whatsit.

[MetroMPG]

bluetwo: pulse and glide was invented decades before hybrids hit the market.
FYI, see: http://metrompg.com/posts/xfi-pulse-and-glide.htm

As dcb points out, it just takes a bit more fussing in a non-hybrid.

In a hybrid, lifting off the throttle kills the engine. Then you finesse throttle position to ensure you're truly "gliding" (no regen, no battery assist). In a non-hybrid, you kill the engine / shift to neutral.

[bluetwo]

I just hope people will be safe when they're navigating a 2,000 lbs. plus vehicle and realize that most of the laws and guidelines are put into place with the safety of everyone in mind. For the sake of the one driving and for all everyone else young and old think about what you're doing before you take an unnecassary risk while trying to set a hypermiling record or whatever by killing the engine at speed in a car that was not meant to be driven that way

[dcb]

I think you may find that the folks who take it seriously are paying a LOT more attention to the road and especially to potential obstacles than your average driver. But always practice new techniques in a safe place, and always THINK.

Personally I wish people cared more about folks who text and engage in other distractions while driving.

[tasdrouille]

I have to agree with dcb. When you are hypermiling, your results mostly depend on your ability to be constantly aware of the environment your evolving in and anticipating what is going to happen all around you. I don't see any real danger going down the road with the engine off when you know exactly what's happening (limited vacuum reserve, heavier steering at slow speeds (if it's not electric)), and see what's coming.

[JacobAziza]

Not only that, but excessive speed is the single largest contributor to injury and fatality accidents, and you won't see many hypermilers guilty of that

Neapolitan: Slow down. My philosophy for life also applies to the road.

[tasdrouille]

Thanks for reminding us Jacob. I wrote a piece on my blog (in French) some time ago about speed limits. During my research I came across a very interesting synthesis of safety research related to speed. From this source, we can see that for every variation of 1 mph in the average traffic speed of travel, there is an associated variation of roughly 4% of injury and fatal crashes.