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2004 Seville SLS
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34 Posts
Discussion Starter #1
A catalytic converter, I mean! :)
My '03 SLS with 129,000 miles has been burning oil since I bought it nearly 2 years ago. When I take a road trip, it doesn't burn any, but with stop and go city driving, I go through nearly a quart a week. Now I'm getting the "service engine soon" light and Autozone's code reader says it's something with the catalytic converter. I've seen the codes in other posts, I just don't remember it.
Replacing the cat is cheap if I do it myself, and I can, but if the burning oil kills the working of the converter, am I throwing money away?
Also, I live in a state with no emissions testing.
Thanks in advance!
 

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White Diamond '03 DHS (with DTS floor shift)
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86,792 Posts
Forget AutoZone and pull your own codes. See the DTC Sticky.

Early Northstars burned more oil than normal and never seemed to have CAT related problems do I wouldn't necessarily blame it in that, but a qt per week is a lot. Read up on oil consumption in the Technical Archives at the upper left of the page.
 

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1999 STS - diamond white
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5,229 Posts
Yeah, the bigger question is why so much oil on a car with so few miles??? That's over $200/year. Forget the cat and do some homework :)
 

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2004 Seville SLS
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34 Posts
Discussion Starter #5
I believe it's the valve guides. It does leak just a bit of oil on the driveway, but it's a couple of drops. Maybe a quart a week is a bit of a stretch, maybe a quart every week and a half. If I stomp on the throttle, my exhaust looks like a diesel. No joke! I smelled the exhaust before I bought the car, and it smelled fine. I had it checked out with a reputable mechanic and besides wheel bearings and struts, it passed. I've since taken it to a different mechanic to give it a once over and he came back with the same bearings and struts issues.
I've driven it on long road trips, 500+ miles and it burns no oil. But commuting every day, I can smell it when I start it. So, the consensus is that burning oil won't kill the cat?
 

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2003 STS w/BoseNav, 1993 Deville, 1985 Deville
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1,089 Posts
I don't think oil burning causes cats to die. When the cat gets hot, it all burns off anyway.
 

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2004 Seville SLS
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34 Posts
Discussion Starter #9
I took my car the Caddy expert in town and he says the burning of the oil is probably from rings and says that would be the main culprit in the imminent death of the cat.
 

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2011 Crown Vic LX, 2009 Chevy Malibu 2LT
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5,607 Posts
I believe it's the valve guides --- If I stomp on the throttle, my exhaust looks like a diesel. No joke! I\
That would point more torwards a ring problem than valve guides. Stomping on the throttle creates high cylinder pressures, but low vacuum. If it smoked under high vacuum conditions, like decceleration with the throttle closed, then valve guides would be suspect.
 

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2004 Seville SLS
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34 Posts
Discussion Starter #14
Yeah, that's what my caddy mechanic said. He believes cleaning the fuel system and soaking the cylinders to loosen the rings could lessen the amount of oil burned and unburned gas that's going through the system. He thinks a combo of this is what's killing the cat. He says BG 44K will work for the fuel system.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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26,323 Posts
Cleaning the fuel system and getting rid of carbon buildup have nothing to do with unburnt fuel.

Go to the black tab at the top of the page, and click on Cadillac Technical Archives. Read the ENTIRE page, LOTS of good info. Pay particular attention to the sections on oil consumption, and why occasional WOT is beneficial to your engine.

As far as keeping the fuel system clean, use top tier fuel (google it), and/or use a 20 oz. bottle of Chevron Techron every 3K-5K miles.
 
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