C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Gas Mileage

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Old Oct 6, 2001 | 02:28 PM
  #1  
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From: Millington mI
Default Gas Mileage

My gas mileage has dropped off about 5 mpg lately.

What kind of things could be causing this?
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Old Oct 6, 2001 | 03:11 PM
  #2  
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Default Re: Gas Mileage (Bradley3)

driving faster
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Old Oct 6, 2001 | 03:48 PM
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From: Millington mI
Default Re: Gas Mileage (Bradley3)



That'd do it.

But I used to get low to mid 30's when cruise was set at 50-55

Now I get about mid 20's at the same speed. My average for a trip used to be about 25, now it's around 19.

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Old Oct 6, 2001 | 04:37 PM
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From: Phx/but its a dry blast furnace kinda heat AZ
Default Re: Gas Mileage (Bradley3)

You can actually set the cruise control for 55... and it works??? :D
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Old Oct 6, 2001 | 05:32 PM
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Default Re: Gas Mileage (Bradley3)

I am going through the same thing and the consensus on the forum and with all my buddies is that it is most likely the O2 sensors. I have 2 on order from Jeff Kopp and will be installing after I am done my travel for the next 2 weeks.
If this is the ticket, I will definitely post about it.
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Old Oct 7, 2001 | 12:08 AM
  #6  
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Default Re: Gas Mileage (MCPOWHITE96)

Quit leaving her in 2nd gear :D... try 3rd or 4th.. hehe
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Old Oct 7, 2001 | 12:30 AM
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Default Re: Gas Mileage (Bradley3)

I would suspect either O2 sensor or not going into closed loop due to bad coolant temp sensor. A scan tool will show the way, although you could check the coolant sensor with an ohmeter to see if resistance varies with temp. Also if you put it into field test mode the SES should flash at about 1Hz when it goes into closed loop.



[Modified by 65Z01, 10:32 PM 10/6/2001]
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Old Oct 7, 2001 | 12:50 AM
  #8  
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Default Re: Gas Mileage (Bradley3)

if it were an O2 sensor wouldn't my check engine light be on?
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Old Oct 7, 2001 | 01:15 AM
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Default Re: Gas Mileage (Bradley3)

I believe you're right about some failures but I don't know all about that device. Anyway, check to see if the ECM is going into closed loop mode.
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