I have a 2005 Pontiac Bonneville GXP with a Northstar V8 in it and it has been using a half a quart every 4000 miles. I use Mobile 1 High performance oil in it with a K&n oil filter. I dont see any oil on the ground or any blue smoke out of the exhaust? Has anyone expierienced this on the Northstar V8 on a Caddy or Bonneville before? I change oil every 8 to 9 thousand miles even though the oil is good for 15,000 miles. The oil looks like new when I change it so Im not really understanding where its going??

When I had my Bonneville it would lose about a half to full quart every 5K which is how often the oil got changed in it. My Impala recently lost 1qt between it last 2 oil changes. same thing your experiencing. no oil on the ground, no staining anywhere. couldn't figure it out.

One very common area of failure is the oil cooler lines on the GXP as well and a few others that don't relate to oil. In my honest opinion your not doing half bad on consumption vs miles. I wouldn't worry about it too hard. every motor regardless of what it is and the age uses some oil over time and miles. and your not to bad in that department. now if you lose a quart in 1000 miles then it'* really time to worry

Here is the GXP
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Thank you so much, that takes some worry off of me because I wouldnt want the bill of rebuilding an engine or maintenencine due to bad valve or piston
rings

ya it'* really nothing to worry about. now when you start loosing more oil in less time that'* when it'* time to say screw it and drop in the 5.3L (you'll like the 5.3L a lot better plus you can play with it unlike the 4.6L)

i agree seems normal. my bonnie as well as every gm ive had goes through between half and full quart between changes. my bonnie ive had for 10 yrs and change the oil every 5k, always has been down a full quart

northstars are notorius for oil consumption, even when not leaking it.

half a quart every 4000 is actually pretty good, i lose about a quart every 2000 or so, mostly through the PCV system.

Doesn't the LS4 have its own oil problems though? lol

ya but nothing like the northstar. and the northstar is more expensive to fix than to just buy a new one

It'* perfectly normal for an engine to consume oil. Even when new, a 3800 Series II is rated to burn about half a quart every 3,000 miles.

I can't imagine a 2005 GXP has too many miles on it, but if it does, you may want to look into replacing the piston rings or valve seals whenever it'* convenient for you. Not sure if either are known problems with aging Northstars; ask one of the Northstar gurus.