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Pontiac Bonneville



  • fgeorge2fgeorge2 Posts: 15
    3,200 miles on mine. Really haven't seen any improvement since day 1. Had 2 SSEi's prior to the GXP - knew the V8 would be a bit worse in the city.
  • montanafanmontanafan Posts: 945
    Did you exceed 48mph average on these trips? That is the average speed in the 10 minute EPA highway mileage test. Was the car fully warmed up when you started? It is in the EPA test. Did you do the run without having to idle the engine? It dosen't idle in the EPA test. I think I even recall that the EPA figure is arrived at by measuring the exhaust output, not the gas used. The EPA test isn't intended to give you and idea of the gas mileage you may get on the car the numbers are on. It is so you may compare the relative gas mielage of different cars, knowing they were tested under the same conditions. And I wouldn't consider it "advertised", as much as post per federal regulations.

    Another variation sometimes would be using a trip computer vs. actual calculations.
  • bunky36bunky36 Posts: 94
    Nothing had changed on my rotors when I took it in to the dealer--they looked the same. I showed them the photo of your rotors. They said your rotors obviously didn't get coated properly and they would do the same as your dealer did--repaint them. They said the coating on my rotors was fine and that what I had was a little surface rust mixed with brake dust that was coming off the new braking surface. They said it won't get any worse now that the braking surface has been established, and that some acetone would remove the surface stuff that I didn't like. They put some acetone on a rag and sure enough it came off. So I went home and removed it all using my wife's nail polish remover (acetone). That was a week ago, and everything looks fine so far.

    While I was at the dealership (a Cadillac, Buick, Pontiac dealership), I checked out several cars on the lot. I found the same thing on all Pontiacs and Cadillacs, but, interestingly, not on any of the Buicks. They also had a GTO in the showroom that showed no rust on the rotors, but the area coated silver on the GXP was black on the GTO. That might be another solution if the rust comes back--the black also made the GTO silver wheel stand out pretty well. We'll see what happens over time.
  • bunky36bunky36 Posts: 94
    I have 1,200 miles on mine but all I've done is city driving so far. I get between 17-18 mpg. Not as good as the 21 I used to get on the SSEi, but about what I expected. I have some highway trips planned for the next couple of months. I am expecting 24-25 @ 70-75. Sounds like I might be disappointed.
  • rayainswrayainsw Posts: 2,476
    GXP highway mileage

    Looking at some numbers . . .

    GXP final drive: 3.71

    4th gear O/D ratio in MX0 / 4L65-E? (also used in new ‘Vette): 0.70

    Optional (performance) final drive ratio ’06 ‘Vette: 3.15
    (I wonder why a 3.5 to 3.7 is not even available on the GM performance flagship?)

    Hmmm . . . 17% deeper overall ratio, assuming similar sized (rolling diameter) 18” tires = significantly higher rpm at cruise.

    Corvette EPA highway: 25
    (And anecdotal evidence suggests that number is attainable.)

    The ‘Vette weighs less and is more aerodynamic.

    17% less fuel mileage than the ‘Vette would equal approx. 23.25 mpg.

    Still not as bad as you are reporting.

    But does make a case for a 5-speed automatic – with a wider ration spread.
    - Ray
    Wondering if no 5-speed automatic for high torque FWD applications means GM has decided that all performance cars will be RWD / AWD – and what that might mean for future of the G6 and GP / GTP???
  • evandroevandro Posts: 1,108
    The final drive ratio doesn't help the mileage and it might be the actual culprit (plus lower efficiency around town of a V8).

    PS: FWDs use the 4T65-E, not the 4L65-E.
  • rayainswrayainsw Posts: 2,476
    "The final drive ratio doesn't help the mileage"
    - Ray
    Still hoping 24+ mpg is possible on the highway . . .
  • fgeorge2fgeorge2 Posts: 15
    Has anyone tried this stuff? I just bought some - they have a website at Anyway, the first stone chip just appeared recently on my hood. You use the manufacturers touch-up paint to create a very slight blob at the site and after it dries, smooth the area with the Langka liquid applied to a t-shirt rag wrapped around a blue "credit card" in the kit. After some patience, the recess is filled and the surrounding area is untouched and blob free. According to them, only works on lacquer touch-up paint - doesn't work on OEM clearcoat.
  • bunky36bunky36 Posts: 94
    I have used it for about three years now. It works very well--not so well that you can't tell where the chip was, but a lot better than just putting a blob of paint in the chip and calling it done. It does a good enough job that someone looking at the car who didn't know where the chip was would likely not see it. And it doesn't affect the surrounding clearcoat like they say. One lesson I learned: when they say let the blob dry, they mean it. So I let it harden for a couple days before I use the stuff. If you don't, it will just take the whole blob out of the chip and you are back to square one. I found that depending on the depth of the chip, in a day or two the touch-up paint usually settles into the chip such that it requires another blob or two to eventually get the blob a little higher than the surrounding surface. So it's not a fast process if done right, but it looks pretty good when you're done.
  • fgeorge2fgeorge2 Posts: 15
    Appreciate the post - gives me some comfort now to try it.
  • ezraponezrapon Posts: 348
    as a former T/A owner, you fully understand the rumble of which I speak. I used to leave the engine run as I filled up my LS1... better than the Monsoon. The GXP was rather quiet at idle. I do miss the toys my SSEi had; the HUD, memory seats, DIC, and auto locking. The G-35 (black coupe) has a build quality GM will never get close to, but has a bit of a harsh ride and is very close in the interior. The G-35 has a better balanced stereo, much more agile, but it too has a funny exhaust note. Snickle... Good to see ur post...long time, back in the day of Intense and his pro street SSEi. My SSEi was a service dept's dream. 18 visits. Sold it the week after the warranty expired. I think the steering shaft was bad at the time... sold it to the dealer who sold it to me...only fair.
  • hammen2hammen2 Posts: 1,313
    The discounts on the new GXP are getting ridiculous. I had my wife's GTP in for service yesterday and was sizing up a new GXP (blue, XM, HUD, sunfoor, heated seat) which stickered at over $38k. There's $5k factory rebate, plus another $1k for GM card holders, who can use up to $2750 GM card dollars, and then there's the GM In The Driveway certificates I can get which knock a sizeable chunk of change off the list price. Bottom line, I can take a GXP home (no trade, not including any down payment including TTL) for a little over $28k. I'm going to take a test-drive tonight...

    I'm tempted, but I'm really about 6 months early (just finished paying off my '98 Aurora). I don't know what interest rates are going to do over the next six months, but, after seeing a co-worker's new 300C at lunch, I'll come right out and say that the GXP is overpriced for what you get. I'm not a huge fan of the front end of the 300C (though it's Bentley-esque look is growing on me), but the interior is very nice and it's got loads of power. Loaded, the sticker on his was $34k. I'm not buying one, though :-)

    I probably will hold off until later this year, saving up my $$$, and hope the incentives stay high like they are now.

    who also thinks the new STS is in a little trouble compared to the 300C
  • evandroevandro Posts: 1,108
    I hope that that ugly body conquers many buyers. Then we might start getting the competition offering full-size, high-power V8 sedans in a price range for peasants like me.

    Of course, it'll be easy for others to better the 300C in style: it's hard to be uglier than that... thing.
  • cglassercglasser Posts: 3
    Thanks to all who replied to my posting about GXP gas mileage. To answer a few of the questions posted by various individuals:

    1) My car had over 1500 miles on it at the time I took the trip. And like another poster noted, I haven't really noticed any change in the overall gas mileage since I got it new with just 9 miles on it.

    2) It was indeed warmed up when I hit the Reset button on the gas mileage display in the Driver Info Center. After 150 miles driving on the highway at 70-75 MPH, it was only getting 19 MPG. My 2002 SSEi posted 26-27 MPG during similar trips.

    3) I understand that the EPA estimate is not really "advertised" mileage, and I guess I shouldn't have referred to it that way. However, as I noted in my first posting, other cars I've owned have always come pretty close to getting the EPA estimated rates - this is the first time the EPA estimates have differed so much from my actual mileage.

    If anyone with a GXP manages better than 22 MPG on the highway, I'd love to hear from you!
  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 17,712
    Have you checked the mileage the old-fashioned way? -- miles driven (odometer and interstate milepost readings) divided by gallons to refill.

    It's odd the mileage is that much lower. My last several GM cars all do much better than highway on interstate or openroad driving. 29 becomes 33; around town 20 becomes 22 even with my wife driving and short trips of 1-2 miles. This is a 3800 engine.

    This message has been approved.

  • evandroevandro Posts: 1,108
    I got new tires on my Bonneville this week to address the infamous vibration at specific speeds (70MPH in my case). So far, so good. It's great to have a smooth ride on the highway again.

    Not a bad deal to get new tires after over 30000mls., expensive tires by the way. Yet, this TSB states that a new lower control arm may be needed for my car's VIN. Let's hope for the better...
  • bunky36bunky36 Posts: 94
    I took a short 400 mile highway trip this weekend from Wichita to Kansas City and back on the Turnpike at a steady 70-75. The car has 1,700 miles on it. Got 20.5 going up and 19.5 coming back. There was a little bit of in-town driving on each end, but not much. Going to take a longer 800 mile run this next weekend up into Nebraska and back. I used to get 27-29 in my SSEi on the same trips, sometimes even over 30 on some stretches. I think getting the GXP to 22 will be a real challenge. While I was in KC, I saw a parked crimson tintcoat GXP. The bodyside cladding was clearly a slightly different shade of crimson than the rest of the car. That would not make me happy if I was the owner of that car.
  • evandroevandro Posts: 1,108
    I assume you've used cruise-control most of the time, right?

    What's the RPM for the GXP cruising at 70MPH?
  • rayainswrayainsw Posts: 2,476
    Bummer - I would be pretty annoyed at that drop in fuel mileage.
    - Ray
    Wondering if there is something mechanically wrong with your particular vehicle . . .
  • bunky36bunky36 Posts: 94
    70 mph rpm = 2250. I think I remember the SSEi being about 1750 @ 65 mph. I really don't think there's anything wrong with the car since others are reporting similar mileage. The facts that it's about 250-300 pounds heavier than the SSEi because of the V8 and the 4T80E transaxle, it has 2 more cylinders to feed, and the 4T80E has a 3.71 ratio versus the 3.05 in the SSEi (I think that was the ratio of the 4T65E in the SSEi) probably explain the drop in mileage. In any case, with the price of gas what it is today, I'd like to be getting better mileage, but all in all it's performing about as I expected. I'm maybe a tad disappointed in the highway mileage so far, but not so disappointed that I'm sorry I bought the GXP. It really is a sweet ride, it looks fabulous, I love the engine/exhaust sound, especially at or near WOT, and it gets lots of attention and looks. Most want to see under the hood. Guess they want to see if it really is a V8.
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