G8 Gt: 30 Mpg?

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Thread: G8 Gt: 30 Mpg?

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    GMI Staff Member FenwickHockey65's Avatar
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    G8 Gt: 30 Mpg?

    I heard that the G8 GT can get up to 30 MPG when running in AFM mode with four cylinders shut down. Could this be true?
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    Re: G8 Gt: 30 Mpg?

    Why not. The Impala SS is capable of it.
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    Re: G8 Gt: 30 Mpg?

    In 4 cylinder mode, your essentially running a 3L V4 am I right?

    I can believe it.

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    Re: G8 Gt: 30 Mpg?

    Seems plausible

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    Re: G8 Gt: 30 Mpg?

    I wonder if you could "double down" on the DOD when its in V4 mode and cut it down to a 1.5 litre V2? Would it be worth a few more MPG?, of course it would only be when the cars was crusing in the highest gear and already at speed.

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    Re: G8 Gt: 30 Mpg?

    If 27+ MPG is easily attainable on the G8 GT, I would put it back on my next car list. G8 Owners: what kind of fuel economy are you getting???

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    Re: G8 Gt: 30 Mpg?

    I have a 2002 4 cylinder, manual transmission Accord. I just drove it across the state of Wisconsin and back in one day. All highway miles, all under 70 mph.

    31 mpg.

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    Re: G8 Gt: 30 Mpg?

    Quote Originally Posted by MCGARRETT View Post
    I wonder if you could "double down" on the DOD when its in V4 mode and cut it down to a 1.5 litre V2? Would it be worth a few more MPG?, of course it would only be when the cars was crusing in the highest gear and already at speed.

    I really doubt that the engine would run well on two cylinders, there would be a lot of vibration and the extra power that they would need to keep the other cylinders moving would probably erase any gas mileage advantage.
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    Re: G8 Gt: 30 Mpg?

    Quote Originally Posted by GMCSonoma View Post
    Is that all???


    My former 2004 Bonneville....3800 Series II/4T65-e/2.86 ratio

    I could easily achieve over 30mpg on the highway going 72-ish..

    My 1998 Park ave...same powertain with 3.05 ratio gets 28-29mpg if careful.
    That's all. And that is about the best I have ever gotten.

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    Re: G8 Gt: 30 Mpg?

    For what it's worth, my 2004 GTO (M6) achieved right at 30 mpg on its first road trip. Driven conservatively I think the G8 should be able to record 30 mpg.

    This past March, my wife and I took the first road trip in our 2007 G6 GTP sedan (3.6 V6, 6A) and got a hair under 31 mpg.

    The 30 mpg in the GTO went bye bye a few months ago (big cam, headers,etc.).
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    Re: G8 Gt: 30 Mpg?

    If you look at the original post it says nothing about averaging 30mpg on the highway. It asks "can the G8 GT get up to 30 MPG when running in AFM mode with four cylinders shut down". All that means is when your cruising on a flat highway while the G8 is able to keep the motor in AFM mode will it get 30mpg. It's quite possible but it kinda depends on the transmission. Not sure how high the 6th gear is in the auto tranny or how aerodynamic the car is.

    My Monte Carlo SS which seems to be very aerodynamic while weighing less and having a smaller V8 will barely do it. The G8 has a few things going against it but has a better tranny so it's possible. No question about it as soon as it drops out of AFM it also drops plenty below 30mpg. The Monte also shows you real time mileage and exactly when it is in 4 or 8 cylinder mode so it is really easy to see the affects of AFM. It's funny when I hear the GrandPrix guys who don't have the 4/8 guage try and claim it makes a 6-8 mpg difference when you can clearly see exactly the difference while watching both guages.
    Last edited by big swede; 05-23-2008 at 06:35 PM.

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    Re: G8 Gt: 30 Mpg?

    Quote Originally Posted by big swede View Post
    If you look at the original post it says nothing about averaging 30mpg on the highway. It asks "can the G8 GT get up to 30 MPG when running in AFM mode with four cylinders shut down". All that means is when your cruising on a flat highway while the G8 is able to keep the motor in AFM mode will it get 30mpg. It's quite possible but it kinda depends on the transmission. Not sure how high the 6th gear is in the auto tranny or how aerodynamic the car is.

    My Monte Carlo SS which seems to be very aerodynamic while weighing less and having a smaller V8 will barely do it. The G8 has a few things going against it but has a better tranny so it's possible. No question about it as soon as it drops out of AFM it also drops plenty below 30mpg. The Monte also shows you real time mileage and exactly when it is in 4 or 8 cylinder mode so it is really easy to see the affects of AFM. It's funny when I hear the GrandPrix guys who don't have the 4/8 guage try and claim it makes a 6-8 mpg difference when you can clearly see exactly the difference while watching both guages.
    As does the G8.
    Seeing as how my Malibu (yeah I know, about a thousand pounds lighter, but whatever) more or less gets 30 MPG while cruising with a four cylinder, I think the G8 would be similar.
    If the G8 does get 30 MPG in AFM mode, that would make it a pretty good road trip car fuel economy wise.
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    Re: G8 Gt: 30 Mpg?

    Quote Originally Posted by FenwickHockey65 View Post
    As does the G8.
    Seeing as how my Malibu (yeah I know, about a thousand pounds lighter, but whatever) more or less gets 30 MPG while cruising with a four cylinder, I think the G8 would be similar.
    If the G8 does get 30 MPG in AFM mode, that would make it a pretty good road trip car fuel economy wise.
    I'm sure it would make a great road trip car. I drove to a vacation last year in my Monte that had our Mustang coasting in on fumes the year before and I had only used half of a tank. I was shocked and after owning the Monte for over a year I feel that is where most of the gains are achieved because it is about the only place you can stay in 4 cylinder mode for any length of time.

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    Re: G8 Gt: 30 Mpg?

    Quote Originally Posted by HoosierRon View Post
    I have a 2002 4 cylinder, manual transmission Accord. I just drove it across the state of Wisconsin and back in one day. All highway miles, all under 70 mph.

    31 mpg.
    That's terrible!!

    Our '92 Accord with a 5 speed gets 34mpg on the highway routinely.

    Put some air in your tires!
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    Re: G8 Gt: 30 Mpg?

    My 02' Tacoma gets 26 at 75mph. My old Honda Prelude got 28 at 80mph and 32 at 70mph (way above EPA). So, if you are anywhere near 30 in a V8 or V6 that is pretty good but not good enough. I know we can do better.

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