Does down-shifting use more fuel?

The put-it-in-neutral-and-coast advocates should get in touch with the people who design automatic transmissions. Those trannies don't drop into neutral when you tap the brake pedal; if coasting made sense, they would. Coasting is dumb. Coasting on hills is specifically illegal in some states. You don't have control. You save nothing. You accelerate pad wear because you're putting all your braking on the service brakes. Maybe you wear out clutch/gearshift lever/auto trans by constantly shifting into neutral (JK -- sort of). Why work that hard?

Using Jakes (or exhaust brakes or transmission brakes) to slow down and to add braking power to service brakes is not "wearing things out." That's what Jakes are for. That's why they were invented. That is why they're called auxiliary brakes. They're durable. You don't not use machines or tools because you'll wear them out. The more braking ability you have, the better. This is so simple even a caveman ...

Coast to save fuel? How much? Five gallons over the life of a vehicle?

 

Okay, so I exaggerated.

 

Don't forget drafting big trucks to save fuel.

 

In 8 pages I haven't seen one mention of this: being in gear all the time happens to enable you to immediately accelerate if needed. Coast and that option is off the table while you're fishing for a gear. Could come in handy if you need to swerve around something because you can't stop fast enough. Oh wait.. that would be being in complete control, right?

 

WHAT HE SAID! (yeah, I'm yelling )

Here's a test. Get on a flat place. Accelerate a bit. Take your foot off the gas pedal/throttle. Shift into neutral. You start to roll faster, don't you?
Engine RPMs will drop but have nothing to do with the speed of the vehicle.

Now stop. Accelerate again and take your foot off the gas pedal/throttle. Leave 'er in gear. You start to slow down, don't you? That's compression, even in a gas engine, and that's why shifting into neutral is a waste of time and effort.

Whew! Are we there yet?

 

Shutting off the truck and coasting on downhill sections saves fuel too, but only a complete moron would do that as well.