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Old 09-24-2011, 12:45 AM   #19 (permalink)
tim3058
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Join Date: Sep 2009
Location: Northeast
Posts: 147

Silver Bullet - '86 Chevy Camaro Z28
90 day: 19.74 mpg (US)

New Blue - '96 Chevrolet Camaro Z28
90 day: 20.46 mpg (US)

Diesel - '96 Chevrolet Tahoe LS
Last 3: 13.56 mpg (US)

Tahoe #2 - '95 Chevrolet Tahoe LS
90 day: 13.05 mpg (US)

SuperDuty - '08 Ford F-350 dually Lariat
90 day: 9.34 mpg (US)

Fundai - '09 Hyundai Elantra
90 day: 26.45 mpg (US)

HRV - '17 Honda HRV LX
90 day: 31.39 mpg (US)
Thanks: 7
Thanked 18 Times in 12 Posts
Quote:
Originally Posted by Joe1234 View Post
Why would you coast with the clutch engaged? Makes more sense to disengage the clutch so the engine can drop to idle RPMs.
When coasting with the clutch engaged the car's momentum is pushing the motor to continue turning. The Civic computer senses this and cuts all fuel to the injectors, creating a "dead" engine until you touch the gas or put the clutch in, idle rpm or not (called deceleration fuel cut-off, or DFCO). Not all stick shift cars cut the fuel on decel, but Civics do. If you were to put the car in neutral or push the clutch in the computer would continue to pump fuel to keep the engine at idle. DFCO can really bump up your mpgs going down a long hill or where you can decel slowly without ticking off other drivers.
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