Share your thoughts good /bad between a GXP Bonneville and GXP Grand Prix 2004 - 2007 vintage. I'm well versed on the Bonneville, owning three, but I only had a Grand Prix for a few months.

Only buy a Bonneville GXP that has had the t-sirt update to the heads. Even then, the GXP is very painful to do any engine work.

I would only buy a 2005 Bonneville SLE. Almost all the exterior looks of the GXP, but super easy to maintain. Lots of engine mods available for the 3.8 if one is interested.

I perform all my own work and as one person said the Northstar is like a size 10 in a size 5 dress. What is the t-sirt update?

The bolts that secure the heads to the block come loose on Northstar engines, causing the head gasket to fail. Not if- but when, often around 100k miles. The engine needs to be remove to fix, and on the Bonneville GXP the engine needs to come out of the bottom- not from above. A major issue for DIY mechanics.

Here is a link with some info:
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the northstar is a terrible engine for working on, repair, lack of mods,and its known for breaking all the time. i would never buy one. the ls4 in the gp is a good reliable proven engine, but still 20lbs of crap in a 5lb sack. i would agree with the sle being the best. i have the 98 version with every option but the l67. the l36 has plenty of power to get you in trouble but gets way better mileage and is way easier to maintain than any 8cyl.

go 6cyl over Northstar any day....

Id take anything over a northstar. Heck Id take a 6.5 diesel over a Northstar.

I have an 05 CadbSTS and the NS in that is awesome. seems as if the 2005 was when they got the bugs fixed. But I have to agree concerning the Bonneville w/3.8. Easiest modern car to work on and they are generally very dependable. I drove an 00 SLE to 243K, and I had removed the insides from the cats, which made it run even better. It never burned any oil(Mobil one)that was 4-5 years ago and I still see it now & then. I still have an 02 SSEi w/110K. Great cars.

I say this because I just had to end my romance with a 1999 classic Olds Aurora... I know well that North Star with all its issues and uncompromising demand for ACdelco and 93 octane gasoline .. she was top tier alright .. I feel nutty now how I have thought a few times a day how the new owner is getting acquainted with the comfort of those power seats.. Yup it acted up on me coming back from a dutiful errand,misfired, and sputtered 1/2 mike from home.,, The trunk leaked and I had just taken the tarp off ..and fill that 18 gallon fuel tank while I was out and evened my tire pressure in each tire.. I know I sound like I am being considerat and attentive to a chick ... it was unrequited love of this I am sure.. It always needed to be nurtured and pampered.. all those miles together became a caretakers commitment...I am falling for the 07 Pontiac Grand Prix GXP model.. We've been acquainted now since April 13. ..for certain... finding another to forget the other seems exactly what I did consistently .. Driving this GP can compare to being on a car date... My girlfriend was been drawing these comparisons and teasing me... I laugh harder cause my car is SO personal. .. I would make folks wash their hands before leaving the tavern after lunch ..No greasy hands wiping my interior with nachos or chicken wings. I had a rule about fountain soda.. the cups with the ice sofa and straw... a dear friend let a large cherry coke slip from her hands and it was everywhere ...Any one else got a car romance and a commited relationship ? Enjoy the day.