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Pontiac Grand Prix GXP 2006



  • rmozolrmozol Posts: 124
    As far as break-in oil, there's different views on that. The first one says to change it after the initial fire up, just for the reason you stated. The next one says change it after about 500 - 600 miles, and then longer after that. Then there's the test that Consumers Report did a few years ago on New York taxi engines. They did some VERY detailed tests, and found that changing the oil AND filter every 7500 was just fine. Engines are made a lot better today than they were years ago. Now, most car engines would shame a race engine from many years ago due to technology. I feel every 7500 is more than ok for a street engine. Hope another opinion helps! :)
  • rmozolrmozol Posts: 124
    Sorry, I forgot about performance mods. Chevy Hi Performance magazine is doing a monthly improvement of a 5.3 Vortec. I don't know if the LS 4 is the same or not though. They did the usual; air box mods, air filter, rocker arms and springs and got a healthy increase at the wheels.
  • hum....I forgot to write the side of the original summer tire. They are asymetric but I don't know why they did not put the wheels rotation mark. If somebody could show me the righ and the left tire, i will appreciate it.

    There is a mark for my bridgestone LM 22 winter tire but not for the RE050A summer tire even if they are asymetric.
  • Here are the conclusions after my weekend road trip. About 1800 miles overall, 1600 of it highway miles.

    First the mileage: this has me mystified, it varied from 21.5 mpg on most tanks to 25 on one tank ( never to be repeated). This was all interstate highways, no noticeable wind, the only possible difference would be hills. Travel was at 78-82 mph for the whole 1600 miles, except for 20 miles of road construction. To say the least, I was disappointed. I would have took the 25 and been happy, but I expected better than 21.5.

    Ride and comfort: I was happy with the ride and handling and comfort of the GXP, as long as it wasn’t a rough road. There were a couple of stretches of bad highway that had some extremely loud tire noise. But overall, I cant complain too much. The seats were comfortable, that 8-10 hour stretch of the drive got to be a bit tiresome, but they always do no matter what vehicle I have driven. Although not what I would consider terrible, the road noise was more excessive than I had hoped it would be.

    The monsoon system… it’s ok.. the sound, especially the bass has a muddy sound quality to it. It is not crisp, at highway speeds you need to have it louder to hear it and the quality goes down with the volume going up. Not as crisp as a Bose system in my Yukon. I was never able to get it adjusted to where it sounded as good as the Yukon’s Bose.

    Overall, it was an uneventful trip, mileage was disappointing, the rest I can live with. Makes me wonder if I should have gotten a 3.9L V-6, but that wouldn’t have been as much fun. I could live with the 21.5 mileage if they put a larger gas tank in it! I hate stopping for gas when that is the only reason I need to stop!!

    Did I mention it is fun to drive and handles well, I may have forgotten with all the other negative things I had to say about it. I am satisfied overall with the car, just disappointed in a few areas. Not enough to not recommend one to others, but enough so that I would tell others the short comings I have discovered.

    Mike :)
  • rayainswrayainsw Posts: 2,935
    Mike –

    0 – thanks for posting!

    A few questions:

    1 – What load? Passengers & luggage?

    2 – Tire pressures?

    3 – At 78 – 82 mph, what led you to expect better than 21.5 MPG?

    4 – Interesting weekend – with 1800 miles driven, did you have any time for anything else but driving? Or did you take additional time beyond the typical 2 days? Just curious. . .

    I would also appreciate a larger fuel tank. Oh, well. When the VW Passat W8 was introduced, with a substantially larger motor than had previously been available, they increased the tank capacity for that model – by 2 or 3 gallons.

    Given the conditions the EPA specifies for their mileage testing, I would NOT expect much more than 21.5 at the speeds you were traveling.

    When I do finally drive my GXP for an extended ‘road trip’ (Thanksgiving long weekend) I will be closely monitoring the fuel mileage, once I clear the Metro Atlanta area – traveling South on I75. Once traffic conditions safely allow it, I typically set the cruise control for speed limit + 5, 6 or 7 MPH, and leave it there. This time once the road levels, I may experiment with some slightly different speeds. To see the effects.

    But with a maximum speed in the EPA ‘highway’ test of only 60 MPH, and with the significant added drag + engine RPM associated with increasing speed by this much (to 80-ish in this case) suggests (to me) that there would be a substantial increase in fuel use incurred.

    A very crude calculation indicates to me that 80 mph vs 60 mph would result in (60 / 80 or 75%) a drop from 27 mpg to 20.25 mpg. Assuming linear increase in fuel mileage related effects as speed rises. Not likely, but the only assumption reasonable without facts not in evidence. And I think that it is at least likely that DoD would be utilized much less frequently if trying to maintain 80 than 60. Point here is only that I’ll bet a steady 80 uses at least 25 to 30% more fuel than a steady 60. YMMV.

    The other factor here may be the temptation to use ALL the throttle travel, when an opportunity (or requirement) for acceleration arises. I find that I certainly do. Where I would utilize WOT in my previous cars, and accelerate to speed for a highway merge, for example, at X mph per second – I now utilize WOT and likely accelerate at X + 25% or more. Achieving desired speed more quickly, but likely using more gas in the process. And then there is the sheer joy of listening to the heterodyne beat of the exhaust as I accelerate – particularly through first gear. (sigh)

    “What's more, the peak acceleration on this test is 3.3 mph per second. This is equivalent to a 0-to-60 time of more than 18 seconds.” – from C+D’s latest ‘Steering Column’.

    Well I know that I ** ONLY ** accelerate at that sort of rate (3.3 mph / sec.) when traffic (or local law enforcement presence) leaves my no reasonable alternative. When I can accelerate (um) quickly, I typically do.

    Further (regarding the linear assumption above) I suspect that product managers everywhere (not just at GM) are heavily pressured to configure & gear & tune & equip cars to achieve the best possible fuel economy on the EPA tests – even if this is accomplished at the expense of some ‘real world’ economy. Meaning, I expect that a product manager would receive positive feedback for increasing EPA ratings by 1 or 2 MPG as posted on the Mulroney Sticker, but would receive no such ‘reward’ for increasing fuel mileage at something near or over the (current, common) highway speed limits – particularly if the EPA ratings suffered. Even though 75 to 80+ is clearly the speed that many consumers actually drive the products.

    Anyway – I am very curious to see what I will see on that trip to see friends on the coast of the Florida Panhandle next week. I will be alone in the car, with a light luggage load, but carrying much beer – several months supply of items not available anywhere near where my friends live . .

    BTW: Somewhat supporting my hypothesis regarding the effect of acceleration on ** MY ** overall gas mileage, I always see a drop (as reported on the DIC display) over the weekend. And most weekends I rarely drive (m)any highway miles. But I absolutely do accelerate. Briskly. The DIC currently reports my fuel mileage as 21.x right now, after a (warm powertrain) fill Monday AM and 1 round trip commute + 1 quick lunch trip + this morning driving to work. (This is approx. 75 miles.) This average will typically fall slowly over the course of the week – and fall quite dramatically, if Friday’s commute home is as bad as it often is. And fall more ‘steeply’ also over the weekend. My guess is that if I filled my tank again on Thursday, eliminating a Friday PM commute and the weekend driving, I’d be comfortably over 20. My overall average (in now over 6,000 miles) is 18.75.

    - Ray
    Feeling that the GXP’s performance vs. fuel mileage balance is OK with me!
    2016 BMW 340i
  • Ray,

    This was actually a 5 day weekend. Two days of driving, 3 days of visiting.

    As for the load, there was just me, about 175 lbs, and maybe another 20 lbs of stuff in the trunk. A pretty light load.

    Tire pressures were set at 31 psi when I left the house, they were checked once after arrival at my destination and were still 31, I checked them, although they were not cold, upon return home and they showed 33, could be from the warm tires, so pressure doesn’t appear to have been a factor.

    I truly expected better than 21.5, I can get 17-18 in the Yukon with the same 5.3L engine and a 3.73 rear gear. The rpm on the GXP was at about 2200-2300 for the entire trip. The Yukon will run close to 2500 at those speeds. With the weight of the Yukon and the extra rpm for gearing, I was hoping for more. It did not seem like DOD was adding as much of a difference as I had expected. It seems as if every GM vehicle I have purchased has came close to the window sticker mileage, and I don’t recall ever having one miss by more than 2mpg below the sticker. I did also keep the acceleration to a minimum. No WOT (no fun for me), and cruise control every chance available. Cruise set to 9-10 above the speed limit, except for the turnpike in Kansas, there it was set 12-13 above the limit.

    Which brings to mind another observation, the cruise does not hold as well as the Yukon. It will vary + or – 1.5-2 mph depending on the hills, especially noticeable going down hills, it will easily gain 3 mph on a big hill.

    It is still a great car, fun to drive, I never saw it downshift once to pull a hill anywhere, which is a far cry from some other vehicles I have driven. Just give me the bigger fuel tank and put a bit more sound deadening insulation in it to absorb some road noise and I couldn’t ask for anything more, except a better radio.

    Mike :)
  • Just joined...enjoyed reading through the previous notes.

    I own a 2006 GXP loaded (no nav.) with 2300 miles.

    Anyway, visited the GM dealer today and did not get much help. I am pretty frustrated about the tire situation.

    I would like to have same size tires front and rear so I can rotate them properly. I am wondering if I can put the same size tires on the rear that is currently on the front without any dramatic impact on handling or the drivetrain. The front tires are about 1 inch wider and very slightly taller profile (if I calculated correctly). So can I put 255/45R18 on rear without problems???

    Also, an earlier posting said that the dealer supplied the buyer with a full-size spare and crammed it in the trunk spare rack. So which spare did you get?...front or rear tire? I figure I might start watching wrecked car lots for a couple so I will have a spare. That fix-flat goop is not the way to go and I may not re-subscribe OnStar, so then if I get a major flat...I am hosed Tommy. This whole tire deal is a real joke is you ask me. For $28K, should not have to worry about it!

    Thoughts on what I should do???????????
  • rmozolrmozol Posts: 124
    You wouldn't be taking Coors Light down that way would you......Bandit??????? :)
  • chats1chats1 Posts: 158
    This morning I've been reading the posts again. And, I think there is a good lesson to be learned here. You don't buy a car when it is first introduced. You wait until it has been out a few years. There seems to be too many issues with this car. I know the Grand Prix has been around for 43 years, but not this one. I agree the Monsoon Speaker System is a piece of junk and I have told GM that. It cannot compare to the Bose System. I am now going to file with the BBB Auto Line re the Monsoon Speaker System. Since GM was aware of the problem in the 2005 GXP, the piece of junk should not have been put in the 2006 model, which I have, or the problem should have been remedied.

    Also, on a lighter note, raccoons seem to find our tires very comfy. One got in my garage when I let my dog out for a minute and got stuck in my rear wheel well -- no damage, thank God, except a small scratch on my wheel. It was a big raccoon. The animal control officer had to get it out. He made me stay inside so I didn't see it and then he let it go!!! It should have been shot. My neighbor is a cop and said if it comes in his yard he'll shoot it. Does anyone know if there is any product that will remove a small scratch on these forged alloy wheels. If so, please tell me. Thanks.
  • For some reason Pontiac seems to be stuck on Monsoon stereos, I have seen it in several other Pontiac models. It is a small step above the base stereo, but not really compareable to a Bose system. If you look through some of the other GM boards, you will hear people who dont think much of Bose either. Good luck with the BBB complaint, I would think that would not go far. Sound system quality will be a higher priority in my next vehicle purchase. Funny how it seems to get overlooked when you test drive the vehicle, but after you spend a few hours alone with the car and the road, all the noises and annoyances seem to surface that you never realized when you took the test drive.

    Mike :)
  • You wouldn't be taking Coors Light down that way would you......Bandit??????? :)

    No Coors Light, and I wouldn't call it Bandit, none of the wheels ever left the ground and the speedometer only reached 90 once, briefly, even though it was extremely tempting on some of that open highway to open it up... I resisted. :(

    Mike :)
  • rayainswrayainsw Posts: 2,935
    "You wouldn't be taking Coors Light down that way would you......Bandit???????"

    Shipyard and Terrapin rye ale or pale ale or Indian pale ale.
    - Ray
    Don’t drink the stuff – just helping an old friend . . .
    2016 BMW 340i
  • I am 32 years old have a wife and 2 children, I still till this day, when I purchase a new vehicle, have an aftermarket subwoofer installed. Nothing crazy, just a single 10" sub to boost the bottom end. My monsoon works great..NOW..
    What's missing is the bass to enhance the music, if you have a home theater system at home then you understand, if you dont, go to a local stereo store and listen to one, it'll cost you about $250 or so for a decent system..INSTALLED..You'll be very happy with a non-intrusive sub placed in the trunk, mine is never in the way permanently mounted and carpeted to go along with the trunk carpet, looks tasteful and sounds EXCELLENT!! Outside of buying a vehicle that costs 50k (most usually morer..way more) you will not find a "GOOD" stereo that can live up to expectations in any vehicle offered ANYWHERE!!
  • Just purchased a new 2006 Grand Prix and I can't figure out how to keep the headlights from coming on automatically in daylight, is that something I can change or do I manually have to click them off everytime?
    Also, with the headlights I was wondering if anyone has had trouble while driving at night oncoming traffic flashing their brights indicating you had your brights on? I have been having that happen a lot.
  • The turn signal stalk on the left side of the steering wheel has the selector knob for the headlights. The manual should provide details on its operation. In the "auto" setting the daytime running lamps will be on during the day but the headlights should only come on when it gets dark.

    Yes, I frequently have been flashed for having brights on when they are not on. However, I do typically also have the fog lamps on.
  • rmozolrmozol Posts: 124
    So Tony, you think that the only thing needed to make the Monsoon sound good is a subwoofer then? I'm pricing GXP's now, and am torn with getting the Monsoon, or upgrading the standard stereo. I also agree that some Bose systems sound good, and others don't. My 2000 Cadillac had one that sounded great. My 2003 Infiniti has the SAME system, and sounds bad. I had to add a 10" sub to that to get it to the liveable level. Are the midrange and highs OK on the Monsoon then? Thanks
  • My GXP is the third w-body car I have owned. If the GXP runs true to form, the front tires will last 14,000 17,000 miles and the rears will last to 70,000 miles. My opinion is that it is not economical to rotate the tires on a w-body due to the difference in tire wear.

    It is even more of a factor re the GXP. Buy the fronts and forget the backs and hope you don't get a flat.

    I also own a 97 Vette coupe and have replaced the run flats with better handling tires (the run flats have very stiff sidewalls). So far no flats yet.

    I don't think that GM had an ulterior motive for the tire selection, in fact the tire selection was very carefully planned. Look at the considerations: front drive, bad weight distribution, aging chassis. My 05 GXP still exhibits some of the bad front drive problems, torque steer, weight transfer off the line. Let me mention that when I hammer my C-5 (Z-51, 6-spd, tweaked intake and exhaust) ya gotta hang on because the back end can get loose.

    Its the same with the GXP. If ya hang on (both hands) yer gonna be smiling when you sail past the Dodge Charger that once was next to you. Its just that the power wheels also steer.
  • hammen2hammen2 Posts: 1,313
    Wow. I've had 2 W-bodies ('91 Grand Prix, '96 Lumina), and the wife's had 2 (another '96 Lumina, '01 GTP). I think the worst mileage I ever got from the stock or aftermarket tires was 39k (when we traded in the GTP, the GS-A's were pretty much done). And I don't drive like a grampa - far from it. Then again, I do check tire pressures and rotate religiously. Typically got 50-60k on tires.

    From what rlsedition has posted elsewhere, the tire consideration was getting the best performance they could - hence the staggered setup and GM working with Bridgestone on the design of these tires - yet making sure they were OK to drive in winter.
  • As I have written in previous posts I really am happy with my 2006 GXP. However I was not aware that it had no spare until reading some of the previous posts. I also feel for a sticker of 34,000,that a spare should be included.The monsoon stereo is just not what I expected. I had an 03 GTP with the bose stereo and while I never thought it had sufficient volume, I felt the sound was reasonably good for a stock stereo. Again for the price of this car they could have engineered a better sounding sound system. I also have had reception issues with the XM {big waste of money so far] and also my FM. The fm does not seem to have a high enough capture ratio and I am also not pleased with the signal to noise level. CD player sounds pretty good but I agree it does need a sub.
  • tlaurotlauro Posts: 504
    if you're asking how to turn off the DRL's, just rotate the ring on the left stalk back towards you. you have to do this each time you start the vehicle, but at least we are able to turn them off. I hate DRL's and pulled the relay in my 99 out. I'll track down the permanant fix for ours in the coming weeks too.
  • tlaurotlauro Posts: 504
    Spare tire wise, you can't safely have a spare when running two different sizes as we are doing. Besides, there's also a brake clearance issue as well, so while I wish we had one too, I think GM did a good job at giving us what they did.
  • tlaurotlauro Posts: 504
    keep in mind the RE050A on the GXP's are not summer only tires. they are a specially designed unit with a specific TPC code on the side for the GXP's. They are a okay to use in snow and were tested by GM extensively as having such a tire capability was a priority of GM's for this car.
  • tlaurotlauro Posts: 504
    the main reason for your big drop in mpgs is due in part to two things....the window sticker ratings and mpg testing that is done is at vastly different speeds than what we typically drive at in this country. the tests are out dated.

    also, when driving at 70mph and above, you're placing a much greater amount of demand on the vehicle and thus DOD is not activating nearly as often if at all.

    I usually drive at 72mph and can watch the DIC and Instant MPG's to see when DOD is active.
  • bob97bob97 Posts: 16
    I guess I’m woofer challenged. I understand how an aftermarket subwoofer provides better bass. But how does adding a subwoofer stop the existing speakers from being tortured by the low frequencies?

    The crossover in a powered subwoofer keeps the highs out of the woofer, but I do not see how this keeps the lows out of the factory speakers? Can someone explain this?
  • also, when driving at 70mph and above, you're placing a much greater amount of demand on the vehicle and thus DOD is not activating nearly as often if at all.

    I will sure keep that in mind in the future, it would seem there would be little use for DOD in a full size SUV. I had thought of a '07 Yukon, but not thinking to much that way anymore.

    I had thought the mileage would be close to the sticker, on every other GM vehicle I have bought, it has been within 1-2 mpg from the sticker. That would have brought the GXP in around 25-26 mpg. I had not given thought to the great amount of added mileage using the CAFE testing procedures, that DOD would produce. Those tests are outdated and if memory is correct, 60mph is the max speed during the test. That would yeild a very impressive mpg rating with DOD. At 20 mph to that and you have the mpg reduced to 21-22.

    It still beats my Yukon by 5mpg, but the Yukon with it's larger fuel tank beats the cruising range of the GXP by over 100 miles!

    I guess if I really wanted fuel mileage, I shouldn't have bought a V-8!! But what fun would that have been.

    Mike :)
  • rayainswrayainsw Posts: 2,935
    I think that part of what we observe here in the GXP is the effect of DoD at higher speeds.

    Or, more accurately, the effect of not being able to activate DoD at higher speeds.

    I have not been able to discover precise published data from GM on what exact conditions are required to allow DoD activation. Clearly it is designed to provide best possible economy under steady state (cruise) conditions, but I expect that the calibrations require (for drivability) DoD to kick off when even a small additional amount of acceleration \ increase in throttle is applied, for example. And my guess is that calibration is optimized for the EPA highway cycle.

    Regarding the Impala SS: “Chevy says the feature could run the Impala V-8 on just four cylinders at 80 mph on a flat road with steady throttle and no wind.”
    (Source =

    So – I expect that if the road rises (even slightly), if there is even a slight headwind, or even slight acceleration is required, DoD is immediately turned off. And the very loose torque converter clutch in the 4 speed automatic, when it unlocks, causes a rather dramatic rise in RPM (700 or 800 rpm in many cases) under most any provocation. This will clearly also impact MPG for the worse. (At least the TCC unlocks very aggressively, both in the sense that it is much easier to provoke and results in more dramatic RPM swings when unlocked compared to my previous 3 vehicles.)

    Where in many other vehicles, you might lose 5% in efficiency under a given set of circumstances (of acceleration, road conditions, headwind) you might lose 10% or more if the TCC unlocks and the DoD is inactivated.

    This is speculation of course, as I do not have access to an SS (with a ‘4 cyl active’ indication) and long, level straight roads with no traffic and a lot of free time (and gas) to conduct experiments. And it appears that GM is not likely to provide verbiage or a graph indicating specifics for us. At the very least, at some point around 80 MPH, under absolutely ideal conditions [[ and at some point below 80 MPH under most ‘real world’ driving conditions ]] the smooth but declining curve of MPG vs MPH likely takes a sharp drop – as DoD becomes unobtainable - and then continues at a substantially lower level of MPG as MPH continue to rise. Actually, it is probably a dis-continuity in the graph – or some such technical term outside my area of expertise. Meaning that the curve is dropping already, but suddenly at some point becomes a straight line down at the “DoD Impossible” point and then continues as a curve, at a lower point – again dropping as speed rises.

    So – it is what it is. This is as close as I have come to an explanation. I have a level of curiosity about all this, but I am not really obsessed.

    And I still really, really enjoy the V8’s acceleration and sound.
    Though that sort of behavior (no speculation here) decreases MPG – a lot!
    - Ray
    Still planning to do a little experimenting on my tip to Florida next week . .
    2016 BMW 340i
  • I have noticed that in almost all reviews that the GXP is most often compared to the Dodge Charger. Did anyone test a Charger yet? I am curious how well their MDS (multiple displacement system) works compared to the DOD on the GXP. I know the Charger priced slightly higher and had lower estimated gas mileage. I really wanted a front wheel drive for winter driving, so the rear wheel drive Charger was never an option anyway, just curious what everyone thought about it compared to the GXP.
  • tlaurotlauro Posts: 504
    I drove a charger R/T....ugly orange one with decals everywhere. DOD in both is pretty much transparent. I never noticed it in the Charger and over the past couple weeks with my GXP....the only way to tell it's on is to watch the DIC and Instant MPG's.

    Overall, I passed on the charger for a number of reasons, but mainly looks and handling.

    It corners like Jello in comparison and while it's powerful and feels fast, I've not seen them turning better than mid to low 14's in the 1/4mi. GXP's are now regularly in the 14.1 range and many who launch them correctly are at 13.8's consistantly.

    The charger looks best on the front, but the other reason I turned it down was the outside is just plain ugly to me. Nice inside, but it's still a Dodge.

    My two cents.
  • the only way to tell it's on is to watch the DIC and Instant MPG's.

    This is true, and you will notice at highway speed, a slight hill will drop the mileage significantly.

    On another note, I think if it did hold the DOD for a longer period of time, we would all be complaining about driveability problems. It might pull that hill with 4 cylinders, but would it do it without downshifting to 3rd gear? That would eat up more fuel than dropping out of DOD does.

    On that note, the driveability of the DOD has been accomplished remarkably. It is 100% unnoticeable when it kicks in or drops off. If you are not watching the DIC instant mileage, you would never notice. You cannot feel it change at all. GM should be commended for this.

    Mike :)
  • Has anyone actually driven the car with the stock tires in the snow yet? Is is the brakes that won't allow a steel 16" rim to be used. The dealer tried to tell me that a 225/60/16 on a steel rim could be used and called GM Canada to enquire further but didn't get much help. I am wondering what, if anything, should be used for the winter. Please let me know how you are planning on handling "old man winter". :(
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