Fuel Economy Logic

  • Thread starter Thread starter Boz Mon
  • 33 comments
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Sure, coasting down a big hill in neutral is better than coasting in gear if the road is straight and theres room to let the car roll however fast it wants (in other words, hills that won't require extensive brake use).

However, coasting in neutral down a small hill, especially if it's followed by an imediate uphill, is just silly, and wears down your synchros more than it saves gas. The same goes for coasting in neutral down hills on the freeway. Why do it? Just leave the car in gear and drive.

Also, as Blake pointed out and I already mentioned, coasting with the clutch disengaged is just a bad idea, even if you rev-match upon re-engaging it -- holding the pedal down and keeping the clutch disengaged for an extended period of time is bad for the clutch components. That's why people will tell you to leave the car in neutral at red lights. Not to mention your left leg will thank you, depending on how much effort your clutch takes. ;)
 
Wolfe2x7
Good thing we're talking about using the engine for braking, then, which doesn't do anything harmful.

Where do you guys get these ideas?
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sounded to me like people were suggesting downshifting over braking, that's where I got the idea.


And Keef, downshifting is far harder on a drivetrain than upshifting, unless you rev match, and even then, it's still a little harder on it.
Why? the clutch engages faster and harder because it has all the car's weight being thrown against it, hence the THUMP! (and sometimes crack) sound you'll get.
The worst thing you can do to any drivetrain, is letting the clutch engage into a high rpm gear, off the throttle, which is what most people do downshifting.

Wolfe2x7
However, coasting in neutral down a small hill, especially if it's followed by an imediate uphill, is just silly, and wears down your synchros more than it saves gas. The same goes for coasting in neutral down hills on the freeway. Why do it? Just leave the car in gear and drive.

Also, as Blake pointed out and I already mentioned, coasting with the clutch disengaged is just a bad idea, even if you rev-match upon re-engaging it -- holding the pedal down and keeping the clutch disengaged for an extended period of time is bad for the clutch components. That's why people will tell you to leave the car in neutral at red lights. Not to mention your left leg will thank you, depending on how much effort your clutch takes.
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If we're smart enough to put the shifter in neutral at a red light, why arent we when we coast down a hill? sheer curiosity...
 
LeadSlead#2
sounded to me like people were suggesting downshifting over braking, that's where I got the idea.
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Ah, I should have figured as much. Sorry.

LeadSlead#2
If we're smart enough to put the shifter in neutral at a red light, why arent we when we coast down a hill? sheer curiosity...
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Because leaving the car in gear at a stoplight would kill the engine. :lol:
 
DO NOT put your automatic in nuetral to coast down long hills. an auto is internally lubricated by a pump that is driven (usually) by engine speed. your car doing 50 and the pump being driven at idle doesnt bode well for your transmission.

just ease off the gas and use enough to keep your momentum.
 

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