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GM B-Body Forum, 77-79 Caprice/Impala Forum

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    MPG on the 79

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    terry cronk
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    MPG on the 79

    Post  terry cronk on Mon Sep 18, 2017 9:53 am

    I recently installed both the 383 and a 700R4 back to my 3.73 gears.

    There is about 700 miles on the engine/trans combo.

    After a 172 mile trip from 70mph on freeway down to 60mph 2-lane roads a fill up was in order.

    Having had it filled earlier with 1 gallon of 110 and the remainder of 93, it took 9.4 gallons to refill.

    That's 18.4 MPG.   Surprised

    I now will try the Lucas octane booster to the tank and see if it helps any.  Still adding a little 110.

    Anyone else?
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    Fierro51
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    Re: MPG on the 79

    Post  Fierro51 on Thu Nov 30, 2017 6:49 pm

    terry cronk wrote:I recently installed both the 383 and a 700R4 back to my 3.73 gears.

    There is about 700 miles on the engine/trans combo.

    After a 172 mile trip from 70mph on freeway down to 60mph 2-lane roads a fill up was in order.

    Having had it filled earlier with 1 gallon of 110 and the remainder of 93, it took 9.4 gallons to refill.

    That's 18.4 MPG.   Surprised

    I now will try the Lucas octane booster to the tank and see if it helps any.  Still adding a little 110.

    Anyone else?

    i was getting 12ish with the 350 on a quadrajunk and 2.73 rear gears. new plugs coil,rotor,cap as well. on 85 octane


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