# Saving gas going down hill

**URL:** <https://community.cartalk.com/t/saving-gas-going-down-hill/15619>\
**Category:** Maintenance/Repairs\
**Created:** [June 20, 2008, 8:38pm UTC](https://community.cartalk.com/t/saving-gas-going-down-hill/15619 "2008-06-20T20:38:48Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![David\_Brown](https://avatars.discourse-cdn.com/v4/letter/d/bb73d2/32.png) [@David\_Brown](https://community.cartalk.com/u/David_Brown)\
**Post date:** [June 20, 2008, 8:38pm UTC](https://community.cartalk.com/t/saving-gas-going-down-hill/15619/1 "2008-06-20T20:38:48Z")

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Love your show.  
  
 To save gas, I have started shifting into 5th gear when going downhill in my 1993 Subaru legacy with all wheel drive. I know this creates more wear on the brakes. I am thinking about installing a switch that would disable the gas supply, e.g., by disabling the fuel injectors or perhaps just turning off the ignition (to Acc. position) . With no gas supplied, I could use a lower gear going dowhill thereby have less wear of the brakes and use even less gas. Do you see any harm that could result in turing off the gas supply when going downhill??  
  
  
  
 When I asked a car mechanic about this idea he told me that this is already done. When going downhill in gear with foot off the gas pedal (high manifold vacumm) the gas is turned off by the computer. I assumed the gas supplied would be at the idle rate. What do you know??

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**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\
**Post date:** [June 20, 2008, 8:50pm UTC](https://community.cartalk.com/t/saving-gas-going-down-hill/15619/2 "2008-06-20T20:50:59Z")

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Your mechanic is right…With the RPM above idle and the throttle closed, all fuel is shut off.

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**Author:** ![NYBo](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nybo/32/17281_2.png) [@NYBo](https://community.cartalk.com/u/NYBo)\
**Post date:** [June 21, 2008, 12:26am UTC](https://community.cartalk.com/t/saving-gas-going-down-hill/15619/3 "2008-06-21T00:26:41Z")

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In addition to Caddyman’s comments, I would like to add that turning off the ignition will disable power assist for the steering and, after a few applications, the power brakes.

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**Author:** ![Joseph\_E\_Meehan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joseph_e_meehan/32/21_2.png) [@Joseph\_E\_Meehan](https://community.cartalk.com/u/Joseph_E_Meehan)\
**Post date:** [June 21, 2008, 1:18am UTC](https://community.cartalk.com/t/saving-gas-going-down-hill/15619/4 "2008-06-21T01:18:43Z")

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Don’t turn off the ignition. The downsides far outweigh the possible benefits, especially when you consider that NYBo and Caddyman are correct.

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**Author:** ![hilander](https://avatars.discourse-cdn.com/v4/letter/h/d9b06d/32.png) [@hilander](https://community.cartalk.com/u/hilander)\
**Post date:** [June 22, 2008, 4:55am UTC](https://community.cartalk.com/t/saving-gas-going-down-hill/15619/5 "2008-06-22T04:55:49Z")

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I hear this said often and yet I wonder how the engine can still be running with all fuel shut off to it.

discuss…