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GM Fuel Economy Observation

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Old 04-15-2008, 08:28 AM
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GM Fuel Economy Observation

After 8 years+ here, this is my first post in the future vehicle's area

I'm helping one of my girlfriends pick out a new car, She likes the new Malibu LTZ 3.6L and I want to show her the G8 3.6L.

I know the 3.8L was a beast and not the smoothest V6 out their, but it was reliable, had good pickup, and got consistant MPG! I averaged around town 22-24MPG out of my Camaro and I know Impala owners would consistantly get 24-30 MPG.

I look at the Aura (which I sold) and Malibu on Fueleconomy.gov and most owners are reporting 20MPG with a max around 24! I know someone else with a 07 STS 3.6L and she's struggling to get 16-17MPG as hard as she tries! I know the 3.6L is much faster and smoother, but at what advancement if the fuel economy is worse?

Look at the Trail Blazer, the 4.3L was similar to the 3.8- torque, but unrefined, but got consistant 17-20MPG in most applications. The 4.2L is awful! Most owners getting 13-15average? Whats the point of the I6 if the V8 gets the same MPG with much better performance???

Last- Muscle Cars! I bought an LS1 GTO because of the 8 years it was in the C5, 5 years in the Camaro, and good reviews and reputation it had for good performance and decient highway economy! The LS2 was short lived (where did it go?) and now the LS3 has amazing HP, but disapointing MPG highway compared to the LS1. I know the Muscle car war is on, but in these times of increased environmental awareness and innovation, shouldnt the new model get better MPG then the outgoing model? Whats with the G8 V8? It's not a LS2, but a 6.0L with 360HP? (similar to old escalade motor?) Is it a iron motor like the trucks? or Aluminum? Either way, it weighs over 4K and rated 15-24MPG (disapointing for 2008 IMO)

I would say a vehicle like the Tahoe would be an example of more performance and economy when they droped the 5.7L in favor of the 4.8& 5.3L in 2000, but with the 07 redesign it tacked on an additional 500+ pounds!!! It's a good looking truck the 07+ tahoe, but it's like driving my fathers 02 around with 2 fat guys in the back seat all the time!

Rant over, I know this board attracts the type who want performance at any cost as long as it's .01sec faster then the next guy, but with impending threat of cars like the Camaro/ Mustang/ Corvette changing their profile or going away for good in order to meet new emission standards, shouldnt this become more priority before it's too late?
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Old 04-15-2008, 08:41 AM
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EPA rating system for 2008 is different than ~1980-2007, new number are about 10% lower for everything.

We have an Aura with the 3.5L/4spd combo and average about 24-25mpg weekly (50/50 city/hwy) and get 28mpg hwy at 75mph. One would think that the 3.6L/A6 combo could match this.

If you want mileage from a Chevy check out the 2008.5 Cobalt XFE, it gets 36mpg!!
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Old 04-15-2008, 08:46 AM
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I think weight is a big factor. Cars are a bit heavier today than 5-10 yrs. ago.
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Old 04-15-2008, 08:47 AM
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Originally Posted by Z28x
EPA rating system for 2008 is different than ~1980-2007, new number are about 10% lower for everything.
I forgot to mention that I am taking that into account. Most of my observation is on what people are reporting.

If you can get mid 20's with the 3.5L then thats pretty good IMO
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Old 04-15-2008, 08:54 AM
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I have continually sung the praises of the 3.9 in my wife's 06 Impala. A "high-tech" pushrod engine is quite efficient (in real-world driving) in comparison to the 3.6 DOHC engine (with the added frictional losses of driving 4 cams and all those valves). Match the current VVT 3.9 with AFM to the 6-speed auto and you have a terrific powertrain (IMHO). Unfortunately, that's just not gonna happen. Too many people judge a powertrain by cams and valves and not by how it performs in everyday driving. My wife is, thankfully, very pragmatic and told me she flat-out preferred the Impala over the 3.6 Aura based primarily on engine response and performance. Icing on the cake is 26-27 mpg in her daily commute.
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Old 04-15-2008, 08:57 AM
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Originally Posted by Chrisz24
I'm helping one of my girlfriends pick out a new car


You are a better man than I!
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Old 04-15-2008, 09:13 AM
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Originally Posted by km9v
I think weight is a big factor. Cars are a bit heavier today than 5-10 yrs. ago.
I know alot has to do with safety features and suspension advancements, but isnt that going backwards? A heavier car will automatically get worse economy. Some of my friends are suprised I'm not totally digging the new camaro, hopefully it weighs less then I'm speculating, but I think I'd rather buy a used C6 for a more nimble car next. Even my GTO weighs more then I'd like and I notice that disadvantage over my old Camaro.

Originally Posted by routesixtysixer
I have continually sung the praises of the 3.9 in my wife's 06 Impala. A "high-tech" pushrod engine is quite efficient (in real-world driving) in comparison to the 3.6 DOHC engine (with the added frictional losses of driving 4 cams and all those valves). Match the current VVT 3.9 with AFM to the 6-speed auto and you have a terrific powertrain (IMHO). Unfortunately, that's just not gonna happen. Too many people judge a powertrain by cams and valves and not by how it performs in everyday driving. My wife is, thankfully, very pragmatic and told me she flat-out preferred the Impala over the 3.6 Aura based primarily on engine response and performance. Icing on the cake is 26-27 mpg in her daily commute.
I agree! The 3.9L really never made big waves, was it based on the 3.8L? I initially was really hoping that would make it into the new Camaro as the V6, but I think it's on it's way out.

When I worked for Saturn us dealers were always beating back the press who trashed the 3.5L Aura, but LOVED the 3.6L. The 3.5L is a fine engine, I'm sure Z28X will agree! And unless your a total gear head your not going to notice a huge difference between the 2. None the less, if you read any auto press you were told to avoid the 3.5L like a red head step child
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Old 04-15-2008, 09:21 AM
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Originally Posted by Chrisz24
I agree! The 3.9L really never made big waves, was it based on the 3.8L? I initially was really hoping that would make it into the new Camaro as the V6, but I think it's on it's way out.

When I worked for Saturn us dealers were always beating back the press who trashed the 3.5L Aura, but LOVED the 3.6L. The 3.5L is a fine engine, I'm sure Z28X will agree! And unless your a total gear head your not going to notice a huge difference between the 2. None the less, if you read any auto press you were told to avoid the 3.5L like a red head step child
3.9L is based on the 3.5L that is in the Impala/Aura

I think the biggest reason to got for the 3.6 over the 3.5L in the Aura is to get the new 6 speed automatic. 3.5L is a nice, but the new transmission is nicer.

Also wieght is a big deal. A 1996 Corsica was about 2800lbs. 2000 Malibu V6 is 3100lbs. A 2008 Malibu is around 3400lbs.

Given the added weight these new cars are a lot more efficient. A 2007 Aura 3.5L is 300lbs. heavier than a 2000 Malibu yet the Aura gets the same 20/30mpg while putting out 224HP vs. 170HP in the Malibu's 3.1L

Last edited by Z28x; 04-15-2008 at 09:28 AM.
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Old 04-15-2008, 09:31 AM
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Originally Posted by Z28x
3.9L is based on the 3.5L that is in the Impala/Aura

I think the biggest reason to got for the 3.6 over the 3.5L in the Aura is to get the new 6 speed automatic. 3.5L is a nice, but the new transmission is nicer.

Also wieght is a big deal. A 1996 Corsica was about 2800lbs. A 2008 Malibu is around 3400lbs.
I think the trans issues is slowly being worked on, soon they will offer a 2.4L/ A6 Malibu so I assume Aura will do the same. I forgot about that disadvantage.

I remember though actually having some buyers go for the 3.5L/ A4 combo because they felt the A6 shifted too often, and I agree- anytime you gave it a nudge of gas it would pull a downshift. The outlook/ Lambada (whatever) twins are the worst for that!
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Old 04-15-2008, 09:40 AM
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Originally Posted by Z284ever


You are a better man than I!
I'm pretty certain he means friends that are female...
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Old 04-15-2008, 09:43 AM
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Originally Posted by Z28x
If you want mileage from a Chevy check out the 2008.5 Cobalt XFE, it gets 36mpg!!
Check out the second post...lol.
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Old 04-15-2008, 09:45 AM
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Originally Posted by Chrisz24
I think the trans issues is slowly being worked on, soon they will offer a 2.4L/ A6 Malibu so I assume Aura will do the same. I forgot about that disadvantage.
The 2.4/A6 combo will be replacing the 3.5 completely in Aura and Malibu for 2009. There will only be the 2.4 (including an Aura XR 2.4 and Malibu LTZ 2.4) and the 3.6 available.
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Old 04-15-2008, 11:43 AM
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Originally Posted by Z28x
3.9L is based on the 3.5L that is in the Impala/Aura
I'm sorry but have you even look in depth at the two motors? I don't car what GM says, they are basically an updated 3.8 and 3.4. They still leak like hell but with better performance and smoother drive. If you look at the motors you will see they are nothing more than a 3.8 and a 3.4 with some updated designs.
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Old 04-15-2008, 11:58 AM
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Originally Posted by mastrdrver
I'm sorry but have you even look in depth at the two motors? I don't car what GM says, they are basically an updated 3.8 and 3.4. They still leak like hell but with better performance and smoother drive. If you look at the motors you will see they are nothing more than a 3.8 and a 3.4 with some updated designs.

I won't argue that the 3.5 is a freshened 3.4 and not the "new" design that GM claimed, but the 3.9 is also an enlarged and updated 3.4, not an updated 3.8 (3800). The 3800 is a 90 degree V6 - a Buick 350 with two cylinders lopped off. The 3.4, 3.5, 3.9 are 60 Degree V6s. They don't share much other than their transmission bellhousing as they have completely different cylinder angles.
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Old 04-15-2008, 12:11 PM
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Originally Posted by Eric77TA
I won't argue that the 3.5 is a freshened 3.4 and not the "new" design that GM claimed, but the 3.9 is also an enlarged and updated 3.4, not an updated 3.8 (3800). The 3800 is a 90 degree V6 - a Buick 350 with two cylinders lopped off. The 3.4, 3.5, 3.9 are 60 Degree V6s. They don't share much other than their transmission bellhousing as they have completely different cylinder angles.
I havn't got a real good like at a 3.9 yet where I work, almost all are 3.5s if they are the new motors. I thought I remembered seeing that the valve covers on the 3.9 did not overlap the intake like the 3.8s, but I've looked at one that I can remember and it wasn't the best.

I'm just glad they are getting rid of those two motors and hope that the 3.6 and the new a6 auto does a better job of sealing gaskets. We had a G6 and a Malibu in the other week, both with the 3.5. The G6 had just under 50k on it and oil pan was already leaking and the Malibu had barely 7k on it and the pan had already began to leak! Combine that with the 4spds in those things that like to leak out the pans and axle seals, and I'm glad the 3.5/3.9 is going away and so is the 4spd autos in those cars.
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