frequent oil change = cat damage?

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This came up in a thread in another forum I visit:"""wouldn't get too worried about the cat convertor issue. The oil additive that poses a risk to convertors is zinc dithiophosphate (ZDP). This is good stuff, an anti-wear additive. If you overfill your crankcase or change oil too frequently cat convertor damage can result. This is why most auto manufacturers are recommending higher quality oil and longer oil change interval.""" Never heard too frequent changes cause damage, other than financial, what do you think?
 
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Zinc phosphate found in HDEO oils can cause damage to catalytic converters; but I must caution: this is only a theory and I have never been able to get a straight answer out of anyone from BITOG on this issue thus so far. That being said, I can't tell you for sure one way or the other, but to be on the safe side for now, I would shy away from running HDEO oils in a car with a catalytic converter. As far as the frequent oil changes and over filling of the crankcase causing converter damage, I don't buy it. Which forum site did you hear that from, if I may ask? PS. Why the multible quote marks?
 
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oh no, I'm KILLING MY CAT! Hide the children! Ok, ok, so I have a dot on the dippy at the top of the scale that denotes "full". 1/32" above the dot I have the letter "F". The oil line when I pull the dippy is at the "F", but above the dot. Now what??? Have I killed my cat? Man, oh man, right off the bat, I've killed the cat. And on a brand new car no less. [Roll Eyes]
 

cephas

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It was off of a motorcycle site, wildguzzi.com discussion page. The newer Guzzi's seem to be coming with a cat in the system. The thread started out with a discussion on viscosity and evolved into a general oil discussion on contents in oil. I used the multiple quotes to mark what an auto "expert" posted, overkill, sorry.
 
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Oil changes have nothing to do with it. Oil consumption is the problem. If an engine consumes oil containing ZDDP at too high a rate, it'll poison the cat.
 
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It's the phosphorus component of ZDDP that may potentially cause damage, and this is a concern to the auto manufacturers, as they will be required to warranty the cats out to 150K miles. Note - ZDDP is a primary anti-wear additive used in both heavy-duty and passenger car motor oils. Phosphorus will volatize just from the heat & circulation of the motor oil - it's not just tied to consumption of oil past the rings. Frequent oil changes promote phosphorus volatility? It's possible that this practice will potentially keep a higher level of ZDDP circulating in the oilstream. But I think a clean running engine with timely maintenance, and clean burning fuels are more important to the long life of a catalytic converter.
 
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quote:
Originally posted by GoldenRod: Zinc phosphate found in HDEO oils can cause damage to catalytic converters; but I must caution: this is only a theory and I have never been able to get a straight answer out of anyone from BITOG on this issue thus so far. That being said, I can't tell you for sure one way or the other, but to be on the safe side for now, I would shy away from running HDEO oils in a car with a catalytic converter.
My .02... I ran Shell Rotella T 10-30 for 210,000 miles in a Merc Villager (OBD I, 1995). No emissions issues, no cat replacement, and passed a sniff test every two years for the 10 I owned it. Over the life of the vehicle, I did not have to add oil over an OCI. I have a strong feeling that if you choose an oil to minimize wear, and said oil stays where it is supposed to (not past the rings and into combustion in massive amounts) that your kitty will be fine, and stay effective. The extra additives in HDEO can help an engine stay clean, and minimize the wear in gas applications, so have at it!
 
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My 2 Jeep's engines have been getting better "E" test results since switching to a HDEO a couple of years back [I dont know] [Big Grin] ...seriously...if your vehicles calls for a SL rated oil and the HDEO is rated to this catagory don't worry about a dead cat...also if your'e burning enough oil to poison a cat you have to be car shopping soon anyways!
 
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Right, if they are SL rated oils, what should we be worrying about? Any of the known sludger cars can ruin a cat in short order if things aren't monitored. Mine lost it's first cat under the previous owner at 30k miles. I assure you they didn't use an HDEO. Cats are cheap anyway if you buy a universal one. I'd risk it for better oil.
 

Tim

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I agree that if you are not burning oil, it should not matter. I had 275,000 miles of 2,000 mile changes on my Volvo, have 150,000 miles of 2,000 mile changes on my Sienna and 150,000 miles of 3,000 mile changes on my LX-450 and no coverter or O2 sensor issues. Those are my three "high mileage" data points.
 

ALS

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Dang, I changed my oil every 3K miles with dino up to 282K and every 5k to present. My cat finally died around 325K miles. It must have been those frequent oil changes that killed it early.
 
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Cephas- if you hang around the BMW motorcyle boards you'll see a bunch of posts regarding zinc and cat issues. From what I've seen, it really isn't a big deal, and the BMW boxers do pass a bit of oil if they're not parked on the centerstand. [oops- should this be on the MC board [Razz] ?)
 
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I present to you one data point here. A car with 263k miles, frequent oil changes, burns a quart every 2200 miles and still on the original cat. Oil burning won't kill your cat. I think running rich from a bad 02 sensor will kill it much quicker than burning some oil.
 
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