3.6 oil consumption

[edelen]

i have 2 04 cts's with 3.6 motors that consome anywhere from from 1 qt of oil per 1000 miles to 1/2 qt per 1000 miles, that can't be normal,the one with a 112000 miles has had Mobil synthetic oil in it and seems to use the most but the other has penzoil and it does a little better, but i read where other people have been told to modify the pvc system, i would like to have some details on that if possable, I have the skill and the tools to make any modifcation needed, but what i don't understand is why do these motors use oil the way they do, i have a 79 pickup that uses oil but you can see it coming out the tail pipe (blue smoke) you see no blue smoke coming out of these cars, and they don't leak at all, so if there are some secret to this i sure would like to know, retired auto repairman so explain it to me i can understand about anything you tell me. THANKS k9will

[cdgrinci]

Your catalytic converter can disguise quite a bit of burned oil (hence no smoke); you may have a ring or valve problem letting oil get past and into the combustion chamber. A compression test or leak down test seems to be warranted here; your consumption is excessive.

[edelen]

Your catalytic converter can disguise quite a bit of burned oil (hence no smoke); you may have a ring or valve problem letting oil get past and into the combustion chamber. A compression test or leak down test seems to be warranted here; your consumption is excessive.

thanks for your awnser, probaly a leak down test would be best, but do these 3.6 motors have a problem with oil comsumption or is the few that do the people with the problems sqeak the loudest and it seems like the few that do consume a lot of oil in a short time, I did not purchase either car until they had over 90000 miles so i don't know the history of there cars before, but i do no one has had mobil oil put in for years by the records left in the car, my kids drive the cars so it is hard to keep up with miles and oil use, but i have started writing it down and tracking it closer thanks K9WILL

[cdgrinci]

The Service Manual states that up to 1 quart per 2000 miles is considered normal. That being said, I can only relate what my engines uses, which is next to nothing. Granted I have a low mile car (42,000) and put only approximately 5,000 miles per year, but I only change oil (once a year, with Mobil 1) and for the last three years haven't needed to add any oil (at all) and the dipstick reading less than a 1/2 quart down (if that much). Reading through the forum (this one and others) you are going to fine engines (that for one reason or another) use more (in some cases a lot more) oil between changes, but I have also seen others that use the same as mine; you're just going to see variances but the 3.6 does not inherently use oil.

[edelen]

The Service Manual states that up to 1 quart per 2000 miles is considered normal. That being said, I can only relate what my engines uses, which is next to nothing. Granted I have a low mile car (42,000) and put only approximately 5,000 miles per year, but I only change oil (once a year, with Mobil 1) and for the last three years haven't needed to add any oil (at all) and the dipstick reading less than a 1/2 quart down (if that much). Reading through the forum (this one and others) you are going to fine engines (that for one reason or another) use more (in some cases a lot more) oil between changes, but I have also seen others that use the same as mine; you're just going to see variances but the 3.6 does not inherently use oil.

What you said makes perfect sence to me i need to get my book out and see where it says that it could use a QT. per 2000 miles that would not be way out line for lease motors with 5w 30 oil in them, the one cts has a po420 code in it is probaly a converter stopping up from oil use, it is possible unless someone has a better reason i would like to hear from you THANKS k9will

[maddmaxx63]

I have an 04 SRX and I to and using oil. This is my 1st caddy and with 90k on it. I have put on about 200 miles when I got a check engine light that came up as a cam position sensor. I took it to the dealer and was told that is was 4 qts low on oil. and that that is what caused the engine code. As I just bought this I am concerned that the dealer sold me a lemon. After reading a searching on this and other forms I see that the oil consumption issue is very common in the 3.6L engine. Dealer said they would change the oil and do the 500 mile monitor for 2000 miles and then report to GM on it and then he said tey will require a cleaning and then more monitoring, then maybe just maybe GM will authorize and repair under the extended warrenty(MAYBE)

I also questioned the dealer as to why they changed my oil and used 10w 30 conventional oil when the manual and even the oil cap states use only full synthetic. I was very cencered about this but was told that the way it is using oil synthetic was a waste. Is this Normal?

[fairwarning]

I have an 06' CTS with the 3.6 litre and am also seeing very high oil consumption.

The vehicle was purchased with 12,000 miles on it in 07' with the Cadillac certification.

I have always run Mobil 1 5w 30 in it. Never have I seen blue smoke from the exhaust.

I will go through 1.5 to 2 qt's every 1000 miles, this cannot be normal.

[Texas Jim]

I have an 06' CTS with the 3.6 litre and am also seeing very high oil consumption.

The vehicle was purchased with 12,000 miles on it in 07' with the Cadillac certification.

I have always run Mobil 1 5w 30 in it. Never have I seen blue smoke from the exhaust.

I will go through 1.5 to 2 qt's every 1000 miles, this cannot be normal.

Assuming it is still under warranty... take it back to the dealer and let them know...

they will probably give you a form to fill out that tracks oil consumption.

If it is excessive...(and it seems like it is)... they will repair it under warranty.

[Cowpie]

These engines are indeed "consuming" oil, but not in the way that many suppose.  The PCV port is poorly designed, with no baffle, to prevent oil from being sucked up thru the PCV tubing and on to the intake.  My 3.6L "eats" a lot of oil this way.  I have a Elite Engineering E2 catch can on the PCV line.  It captures about 1 - 1.5 oz of oil every 100 miles. That is almost 1 qt in 2000 miles.  Almost mirroring exactly what the consumption rate is, and what many report.   Not exact same amount as the consumption rate, but darn close.

I am looking at a replacement PCV grommet for the valve cover, that has an integral baffle.  Not sure if it would have the clearance or not to be viable option. Still looking into that.

https://m.pepboys.com/product/details/9968578/01036

[Cowpie]

When I picked up a 2006 CTS 3.6L a couple of months ago with 52,000 miles on it, I learned pretty quickly that it was an oil eater.  Dealer had changed oil before I took it, but after a couple of week of some serious consumption, I did an engine flush on the engine and changed oil and filter, using a 5w30 synthetic.   I also put on a Elite Engineering catch can on the PCV line.  As the vehicle was driven, the can collected about 1.5 oz of oil every 100 miles.  Pretty sad.   So after 2000 miles of this, I did another engine flush on the engine, changed oil and filter, this time using a 10w30 synthetic.   Into the second week, and the oil level has not dropped a bit on the stick.  I dumped the catch can at the oil change and have not checked it again since oil level hasn't dropped.  Looks promising.  Over 200 miles since the oil change and oil level staying the same, whereas before it would already be about 1/4 qt low by now .  Not sure if the additional flush finally got rings and channel deposits taken care of or the 10w30 was a major factor, or both.  The 10w30 should not have made that much difference, because a 0w30, 5w30, or 10w30 has the exact same viscosity at operating temperatures.  Only the cold flow is different.  But the 10w30 has a very low NOACK (burn off vaporization rate) compared to 5w30 or 0w30.    Will continue to monitor, but things look much better.

For there to be so much oil coming thru the PCV line, there had to be an excessive blowby issue to contribute to that.  A couple of engine flushes might have got rings unstuck and got them sealing up well again.  Without an engine tear down, there is no way to confirm anything, but seems a reasonable assumption.

[Cowpie]

Second week and another couple hundred miles.  Catch can captured maybe 2 oz total since the oil change, and the level hasn't moved off of full mark.  Think I indeed got a handle on the oil consumption issue.  The consumption decreased dramatically to almost a non existent level.   At this interval after an oil change before, I would easily be a bout 1/2 qt low.  Anyone that has the consumption issue, what I did might be well worth giving a shot. Nothing to lose in trying.

[Bruce Nunnally]

What was the type of engine flush you used?

Were the 5W30 and 10W30 otherwise the same -- same brand, same type within that brand, etc?

[Cowpie]

Yes, same brand of oil, Amsoil XL, just a change from 5w30 to 10w30. I used the Amsoil Engine Flush product, two different occasions, 2000 mile spread.  The Signature Amsoil stuff just doesn't seem like a good value, very pricey, and I have no interest in extending drain intervals.  Now that things have settled down, I will probably stick with 5000 mile oil changes.  The XL compares favorably in pricing to off the shelf stuff (at preferred customer pricing) and has a pretty good add pack in it.   A good bang for the buck.

Took a road trip last weekend.  Now at almost 1000 miles since oil change.  Dumped the catch can last night. The can captured another 3-4 oz of oil from the PCV line. Added to the previous 2 oz it captured, 5-6 oz total captured.  The oil level did drop by about 1/4 qt.   So factoring out the catch can capture, the engine is "using" about 3 oz of oil in 1000 miles now.  Not bad at all.   I did a look up of the EPA estimated fuel economy on this model/engine, and this car is getting about 2-3 mpg better across the board than the estimates.  Pretty darn good for a car that was very poorly maintained for the previous 52,000 miles before I got it.  A real keeper now.

[Keith D]

On 8/13/2016 at 8:27 AM, Cowpie said:

Yes, same brand of oil, Amsoil XL, just a change from 5w30 to 10w30. I used the Amsoil Engine Flush product, two different occasions, 2000 mile spread.  The Signature Amsoil stuff just doesn't seem like a good value, very pricey, and I have no interest in extending drain intervals.  Now that things have settled down, I will probably stick with 5000 mile oil changes.  The XL compares favorably in pricing to off the shelf stuff (at preferred customer pricing) and has a pretty good add pack in it.   A good bang for the buck.

Took a road trip last weekend.  Now at almost 1000 miles since oil change.  Dumped the catch can last night. The can captured another 3-4 oz of oil from the PCV line. Added to the previous 2 oz it captured, 5-6 oz total captured.  The oil level did drop by about 1/4 qt.   So factoring out the catch can capture, the engine is "using" about 3 oz of oil in 1000 miles now.  Not bad at all.   I did a look up of the EPA estimated fuel economy on this model/engine, and this car is getting about 2-3 mpg better across the board than the estimates.  Pretty darn good for a car that was very poorly maintained for the previous 52,000 miles before I got it.  A real keeper now.

Wow great information and you got my dander up now ha.. I have the '08 CTS 3.6 Direct Injection with 60K miles on it and it runs beautifully and as far as I can tell not burning any oil as I have put about 1000 miles on it so far . I actually bought it from an older couple original owner new so I'm sure it has easy miles on it.. I made the mistake of reading into all this oil consumption business way to much now I am thoroughly depressed. I do hear about this PCV problem though that carbon and junk builds up in these 3.6's and that does concern me to. You mentioned a catchcan at the pcv area and I'm sure I want to do something like this soon do you think this is necessary with my situation??.. I'm neurotic about Mobil 1 Synthetic every 3k miles anyway so the oil will be clean along with gas cleaners in the tank to very frequently to try and ward off any of this build up crap that could start so I want to keep engine as clean as possible.. thanks for any info.... I'm a backyard mechanic myself and can do what i need to but would need assistance first with maybe pics somewhere along the line somwehere...

[Keith D]

On 11/28/2011 at 8:10 PM, edelen said:

i have 2 04 cts's with 3.6 motors that consome anywhere from from 1 qt of oil per 1000 miles to 1/2 qt per 1000 miles, that can't be normal,the one with a 112000 miles has had Mobil synthetic oil in it and seems to use the most but the other has penzoil and it does a little better, but i read where other people have been told to modify the pvc system, i would like to have some details on that if possable, I have the skill and the tools to make any modifcation needed, but what i don't understand is why do these motors use oil the way they do, i have a 79 pickup that uses oil but you can see it coming out the tail pipe (blue smoke) you see no blue smoke coming out of these cars, and they don't leak at all, so if there are some secret to this i sure would like to know, retired auto repairman so explain it to me i can understand about anything you tell me. THANKS k9will

 

On 8/28/2012 at 9:52 PM, fairwarning said:

I have an 06' CTS with the 3.6 litre and am also seeing very high oil consumption.

The vehicle was purchased with 12,000 miles on it in 07' with the Cadillac certification.

I have always run Mobil 1 5w 30 in it. Never have I seen blue smoke from the exhaust.

I will go through 1.5 to 2 qt's every 1000 miles, this cannot be normal.

Hello did you ever get your issue solved?

[Bruce Nunnally]

23 hours ago, Keith D said:

 

Hello did you ever get your issue solved?

@Keith D wrote back: No, still about the same.  The vehicle runs strong, but has always burned oil.

[Keith D]

I think your burning oil because your rings are not seating well.. Ive heard many good things about a quart of motor flush right before every oil change and even running a quart or 2 of transmission fluid in your oil for 100 miles, Ive done that numerous times.. Give it a try, it frees up many sticky clogged up things and resolves oil burning issues...