Catalytic Converter & Burning Oil?

[outrun]

Here are the stats, GM 3800 Series II, ~188,00miles, oil burning rate on M1 1.0-1.5qts/3,000miles ... most common is .5qts/1,000miles. V6 Camaro 1998 set-up, single cat.

O2 Sensors, Plugs, Wires all replaced with premium components per conservative intervals. Only current OBDII code is CatCon Low Efficiency.

History: At 90,000miles OE cat started rattling. I made possible mistake by having a local shop put a cheapo 250$ cut-out weld-in universal unit.
Now at 188,000 this aftermarket unit is rattling and needs replacement.

Questions, I have read alot and come to the conclusion that even though the GM OE unit is 400$ that is the best to go for emmissions. Since the exhaust shop cut-out and welded a universal cat in ... does this mean a bolt in OEM unit will now longer fit? Or will they have to weld and fabricate it in?

Second, is my oil burning causing a cat premature failure? The only similar situation is that both cats exhibited rattling at fail time. Thanks-

 

[mikered30]

Oil burning over time will kill your cat, you can get it replaced but after you find and resolve the burning oil problem.

 

[SubLGT]

Originally Posted By: outrun
...............Second, is my oil burning causing a cat premature failure? The only similar situation is that both cats exhibited rattling at fail time. Thanks-


Phosphorous from the oil can reduce the effectiveness of the converter, but I don't see how it can cause rattling.

 

[MrCritical]

The rattling is caused by the cat coming apart inside, which doesn't have anything to do with the oil consumption.

I'd say your rate of oil consumption might shorten the cat life a bit, depending on when the engine's oil consumption is the highest. If the cat is fully warmed up it can take more oil.

There are some folks who swear you can cut oil consumpion by not using Mobil 1. I'd give it a try. At 188k what have you got to lose?

And yes, you'll have to fabricate something to get the bolt on OEM converter back on.

 

[alreadygone]

Originally Posted By: MrCritical
The rattling is caused by the cat coming apart inside, which doesn't have anything to do with the oil consumption.

I'd say your rate of oil consumption might shorten the cat life a bit, depending on when the engine's oil consumption is the highest. If the cat is fully warmed up it can take more oil.

There are some folks who swear you can cut oil consumpion by not using Mobil 1. I'd give it a try. At 188k what have you got to lose?

And yes, you'll have to fabricate something to get the bolt on OEM converter back on.


I'll agree about 99% with this. Usually when I replace with universal cat it takes a pretty observant person to notice!

Question; If uni lasted 90,000 miles, approximately the life of the original, why would you feel the need to go back with a OE that lasts approx same length and costs 3-4 times as much? Universals get a bad wrap they don't deserve!

Bob

 

[dwendt44]

What weight of Mobil-1 are you using?
Texas doesn't get clod enough that 5W is needed. Go with 10W-30, or one of the 'high mileage' oils.

 

[Tosh]

Originally Posted By: outrun
History: At 90,000miles OE cat started rattling. I made possible mistake by having a local shop put a cheapo 250$ cut-out weld-in universal unit.
Now at 188,000 this aftermarket unit is rattling and needs replacement.

Second, is my oil burning causing a cat premature failure? The only similar situation is that both cats exhibited rattling at fail time.

By your own account the universal cat lasted 98,000 miles while OEM lasted 90,000. What's premature about that?

 

[TexasHonda]

Those levels of oil consumption are not bad. I doubt they will affect converter. OEM converter sounds like a pretty fair deal. I would check that all your exhaust system hangers are in place and functioning. Lack of support could cause excess vibration and early damage to a converter.

If oil consumption is exhibited as puffing smoke after a long idle, and a large cloud of smoke as you accelerate after a long idle, the vavle stem seals are leaking oil. These can be replaced w/o removing heads, but still a pretty tough job.

good luck

 

[outrun]

Okay here is my concerns based on your responses. Yes both cats survived the approx same mileage interval before suffering apparent substrate-case separation which caused the rattling symptom.

The reason I have pro-oem feelings for the cat is that many sites and sources argue that the over the counter cats have little precious metal so your only getting MINIMAL catalytic efficiency ... or as said here with a cheapo cat just barely enough to pass the sniffer test.

Now I know either way my car will produce emissions ... but if the OEM cat has higher precious metal composition and superior efficiency vis-a-vis a cheap car sound cat the OEM choice is more environmentally sound right? If Pt, Pd, and Rhodium are trading sky high per ounce, how can a 250$ cat have anything valuable inside?

Of course, my car has never been smog tested so I have no data to prove the Nox etc ppm counts of my car new from the factory and older with the car sound after market cat.

I will check out the rattling through and exhaust clip inspection. Second, can driving on bad roads, and the jarring from bad bumps shock a catalytic convertor over time?

There has never been white or blue-smokeism by my car. I would hate to think that the GM 3800 with all its good reputation would develop internal engine problems already? I really want to know why the consumption is high. I suspect it is the synthetic causing this. At this point I do not want to spend money on a compression & leak down test.

Another question ... Anyone know anything about "Walker" AutoZone's premium OE replacement cat brand? The one they had for my car was a one peice assembly with the Y-pipes built in.

 

[mechtech2]

The rattle may be an external heat shield.
If it is internal, the cat is puked.

 

[Vilan]

I agree that you get what you pay for, but I wouldn't expect a $400 cat to have vastly more catalytic material inside than a $250 one. Could just be differences in markup and volume sold. If the OEM was $1000, that would probably do better than the universal, but then would you want to drop that much?

And since you don't seem to have smog testing where you are, it doesn't much matter which one does better, it's more of a feel-good issue. So that's up to you to decide how important it is to you.