2008 PONTIAC G8 GT

Highs: Tire smoke at six o’clock, German handling, spacious, dashing duds.

Lows: A fuel hoocher when used as directed, shift snap, no nav.

The Verdict: The wizards of Oz pull Pontiac’s performance cred out of the dunny.

Clipped overhangs and sheetmetal that is sucked tight over the wheel arches and cabin give the G8 the crouched stance of a Teutonic high roller. The G8’s skeleton is all-new and 100 percent Australian-developed. At 114.8 inches, the wheelbase is 5.2 inches shorter than a Charger’s and the overall length is four inches less; the width and the height are within a few 10ths of the burly Dodge’s.

Our loaded GT weighed 4100 pounds, fairly evenly distributed, with 48.3 percent carried by four stamped steel and cast iron links in back that replace the semi-trailing arms of the old GTO.

And there’s power, enough to pull quarter-miles in 13.8 seconds at 104 mph. This Gen IV small-block is the L76, a 5967cc V-8 that bellows through its eight-into-two-into-one-into-two-into-four exhaust but lives much of its life as a V-4 to conserve juice. To dodge a gas-guzzler penalty, the cylinder shut-off is aggressively programmed and not altogether transparent. A faint flutter through the steering wheel and floorboard means half the cylinders are asleep. It’s an acceptable trade-off for a claimed 10-percent gain. The EPA says the V-8 makes 24 mpg highway. We saw 18 for one fill-up; the test average was 16.

http://www.caranddriver.com/reviews/..._test/(page)/1

 

That paragraph about cylinder deactivation is telling.

It's the most worthless "technology" GM has foisted on us since skip-shift. They delayed the car over a year, took away the choice of a manual, and ruined the powertrain refinement for nearly a zero gain in fuel economy over LSX powertrains we're used to. This is also why Holden does not use cylinder deactivation.

This car averages no better than all the V8 cars (and trucks) I've owned without it.

What does it take to get rid of cylinder deactivaton? A new cam and a tune?

 

Skip shift allowed cars to pass drive by noise regulation test, I would hardly call that useless. Or you could give up an extra 20hp to quiet the car down more.

 

This car has fuel saving technology that doesn't appear to save anything and creates a noticable judder in the powertrain. I'm not sure how anyone can justify that in any car let alone one dedicated to performance that isn't exactly cheap.

Can this be eliminated as easily as skip-shift?

 

10% highway fuel economy increase may be enough to avoid a gas guzzler tax. If I can pocket that money, it will be worth it. DOD/AFM and even skip shift were games on the government testing to avoid some type of penalty.

Of all the review I have read so far, C/D is the only one to mention that behavior around AFM. Since there is no AFM light to indicate activation, I wonder if it is truly AFM or if it might be TCC lockup.

As for turning it off, I'm sure someone will offer that as a reprogram option with the PCM. Of course, it takes very little throttle movement to turn it off anytime that you would like. These systems are geared around part-throttle, light load, cruising conditions. If I am over 75MPH in my GP GXP, AFM basically never kicks in. So I get around 24mpg. If I stay 70MPH or below, I can knock down 26 or 27mpg. So, I don't think it is useless, just a very narrowly focused item that saved the consumer some money.

Chip

 

I think GM's efforts would have been much better spent refining the economy of the V6 model and not the V8 model people are buying for performance.

Holden already builds this car with a V6 manual as well as an L98 manual, why couldn't they just offer the V6 and L98 manual combo for US buyers and be done with it? Leave AFM and the L76 for automatic customers like Chrysler is doing with the Challenger.

My LS2 is returning 25-29mpg freeway and returns 16-18mpg in traffic which is better than C/D got out of the G8 they drove. The LS2 is always "awake" and ready the split second I put my foot on it.

Edmunds also owns a Silverado with AFM and wrote the following.

http://www.edmunds.com/insideline/do...ticleId=119281

"In everyday driving, the Titan's rapid, linear throttle response made the Silverado's seem stodgy in comparison. Throttle inputs in the Silverado are overly damped, and the general reluctance of its four-speed transmission to downshift is very noticeable.

This Chevy V8's fuel-sipping four-cylinder power mode makes the engine seem even sleepier, and it takes a half-beat for all eight cylinders to wake up when you stab the throttle. From our logbook: "The Chevy's soft throttle response is unfortunate. Also, I'm not sure what the numbers say but this one feels by far the slowest.

Since our Silverado is a long-term test truck, we have a larger sample size from which to cull fuel economy data. The picture is not pretty. Over 5,436 miles, the Chevy has averaged 12.7 mpg with a best tank of 14.2 mpg. Of the three trucks, the Silverado's performance is the furthest from its EPA rating of 15 mpg city, 19 mpg highway."

I've also noticed this same behavoir on Chrysler's I've driven with cylinder deactivation and really hated how it feels. Holden also doesn't use it for the same reasons.

http://www.drive.com.au/Editorial/Ar...rticleID=28748

"The Pontiac G8 GT also has one first over the Commodore it is based on. It features GM's Active Fuel Management system which can cut out four cylinders when they are not needed to save fuel. Holden did not fit AFM to the Commodore at launch, insiders telling drive.com.au at the time that it could not be made refined enough for Holden's standards."

This is why I dislike AFM and why it has me second guessing buying this car. I want a G8 GT but this is nearly enough to scare me off.

 

V6 or V8, you will burn a certain amount of fuel just moving this car around. We are probably lucky GM decided to even offer a manual period. At least they did it where it will be appreciated most. The truth is (and I think you know this too) is that very few manual V6 models would be sold. If they don't sell, it doesn't help CAFE (CAFE is sales weighted after all). I also don't see GM certifying four (six if the GXP was included) different powertrain combinations for such a limited production run (40,000 vehicles is not a lot to spread six powertrain combos across).

As for the trucks, the EPA ratings for most vehicles have been way too optimistic. That is why they were adjusted in 2008. If you go look the Silverado up, the 2007 model with the 2008 calcs show 13 city and 17 highway. Edmunds returned 12.7. My experience has been that I typically return fairly close to the city rating and rarely at the highway rating for all the vehicles I drive. They also do not list which rear gear ratio is on their truck. I know that there are at least three (3.42, 3.73, 4.11) that could be optioned. The gear ratio will obviously have an impact on gas mileage. The EPA does not provide ratings for the various optional ratios.

The throttle response is all controlled through the PCM because of ETC. I think this is independent of whether you have AFM or not. I do not find the throttle response of my GP GXP different from my wife's 2004 Escalade ESV. Both have a slight hesitation especially getting the tranny to kickdown. I find that to be true whether the GP GXP is in AFM mode or not. That could be adjusted aftermarket, but just seems to be a fact of life with auto trannies and ETC. I can't speak to the Chrysler MDS since I haven't driven one so equipped.

I don't believe AFM has ruined the car or should cause someone to second guess. Even Car and Driver said it was worth it. I tend to find them pretty critical of most cars, so that it is almost an endorsement coming from them.

Anyhow, AFM is a tool that can be used to bump your gas mileage by 2MPG on the road if you try. Or you can ignore it and get the lesser gas mileage that you would have without. I have 30,000+ miles with it and have not found it to be obtrusive. The car does what I want, when I want. I can knock 26mpg on the highway if I behave or I can achieve 23mpg on the same stretch of highway if I am really moving (that is about the difference in running 70mph and 85 - 90mph on all interstate highway).

And of course, I am sure the Feds would be happy to accept your $1500 contribution toward the budget immediately if you are so inclined to send money their way. I think I will keep mine and use it for mods.

Chip