Oil that won't clog the catalytic converter?

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15
Location
New England
The catalytic converter on my Prius gets clogged with oil and performance suffers. Is there an oil that will result in less issues with the CAT? I read someplace, that phosphorus and sulphated ash content that is particularly damaging to the cat. Would an oil carrying a rating such as ACEA C1/C2/C3, or a dexos1 or ILSAC GF5 for example help in my situation? It looks like the ratings with the lowest sulfated ash content would be: ACEA C1, lowest SAPS (Sulphated Ash, Phosphorous, Sulphur) or ACEA C4, having low SAPS but a higher HTHS rating. How does API FA-4 rating stacks up? In this 2007 prius with 260,000, I use Walmart Super Tech full synthetic high mileage 5w-30 (& whatever filter is handy) and change at 4,000 miles. I tried a can of CataClean and it made a world of difference, better mileage (back to 49mpg), significantly improved acceleration and best of all the exhaust fumes stayed out of the car (not sure how a clogged cat sends exhaust into the cabin?). Sadly the improvement was short lived and after about a week I was right back to the square one. Other things I may try; replace PCV valve, replace spark plugs, install an oil catch can, an engine flush, use Techron fuel additive for a month, baby the gas pedal, clean the mass air flow sensor, try a higher viscosity oil 10w-40.... If I could just keep the CAT from being clogged I would be all set.
 
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Northeast Nebraska
Can't help with the oil but what concerns me is you getting exhaust fumes in the cabin, clogged cat or not you shouldn't be getting any exhaust in the cabin.
 
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D/FW Metroplex
Once a catalytic converter becomes fouled with oil or " "clogged" with any substance, it's pretty much ruined. There is no helping it or bringing it back to life. But if that were occurring, the bigger problem would be to identify how/why the oil were getting into the cars, then fix that. Normally they won't care what the oil is, as they aren't supposed to touch the oil. For the cats to get fouled that way, there would be lots of other drivability problems afflicting the engine too. Is the CEL illuminated? Does the car idle and accelerate roughly? Any recent service performed on the engine that could be associated?
 

Kestas

Staff member
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The Motor City
The fumes can sometimes get in if windows are open. Wind currents can get funny around cars. Sometimes the fix is to close the windows and keep the cabin fan on.
 
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5,509
Location
Atlanta,GA
Sounds like the engine is worn out due to excessive blow-by. Check compression, if ok, then buy a new catalytic converter or you could just buy a new car.
 

Underdawg

Thread starter
Messages
15
Location
New England
Originally Posted by Kestas
The fumes can sometimes get in if windows are open. Wind currents can get funny around cars. Sometimes the fix is to close the windows and keep the cabin fan on.
The fumes enter the cabin when the vehicle is idling. If the cabin fan is set to "re-circulation" while the car is idling there are no fumes/smell. I've tried plugging up the exhaust and found no leaks and taken in to the shop and they did the same. This issue first started 3 years ago and would only occur if the vehicle was idling while sitting at an incline (nose up). I wondered if the a rear seal around the hatch was letting fumes from the tailpipe in or if one a rubber grommet from under the spare tire was missing (also not the case). I just make a habit of turning on "recirc" if the car is not moving. The only other Prius owner I've found with this problem had a clogging cat so I just assumed the two issues were related. I may be wrong. I would be thrilled to unravel the mystery.
 
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2,330
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South Carolina
Originally Posted by BMWTurboDzl
Sounds like the engine is worn out due to excessive blow-by.
Yes and at 260,00 miles the cat was already toast.
 
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219
Location
Chicago
Do you have any oil loss between oil changes? I would do a cylinder leakage test to see if you have a bad cylinder. Sounds like you need to change the catalytic converter, I wouldn't recommend changing a low ash oil ACEA C1,C2,C3, it's really splitting hairs, those oils tend to have higher engine wear, it's a two fold issue. Do you want to replace your catalytic converter or do you want replace your engine?
 

Underdawg

Thread starter
Messages
15
Location
New England
Originally Posted by nascarnation
Curious, are you getting P04XX codes for low catalyst performance?
Yes, I got the code just before my inspection a week ago. I poured in CataClean (not a fan of snake oils) and passed inspection with flying colors. The code has not come back on but I know it will if I don't do anything. I log 60 miles a day, 7 days a week and this is the only issue I've had (other than the fumes). I've driven my last 3 cars to 350k (not many miles for this forum) and thought the Prius would at least make it to 300,000.
 
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10,629
Location
Jupiter, Florida
Originally Posted by The_Nuke
Once a catalytic converter becomes fouled with oil or " "clogged" with any substance, it's pretty much ruined. There is no helping it or bringing it back to life.
Consider cleaning the cat... I get your point, once the cat goes bad, it's a problem that won't fix itself. However, there are ways to clean catalysts. In industry and especially in aviation, some catalysts are cleaned when performance suffers. Of course, they are not exhaust cats but the method of operation and construction is very similar. A solution of citric acid and hot water can clean an exhaust cat. It's not a fast process, but it often works. Quote: "Scientists at Madrid's Institute of Catalysis and Petrochemistry have discovered that diluted citric acid can remove these deposits without affecting your converter's platinum. Just soak the catalytic converter in a citric acid solution for six hours; and if it doesn't have other problems, it'll be as good as new" Are you consuming a lot of oil? A healthy cat should be able to deal with modest oil consumption. Today's oils don't contain high levels of ZDDP and should be fine with some oil consumption. Maybe the answer is simply an OEM cat.
 
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17,716
Location
NH
My Camry can get exhaust fumes inside the car and I'm not sure how--I haven't found any leak. For a while it smelled like untreated exhaust; last few times more like burned oil. No idea what is causing it, but when it is acting up I just turn off HVAC at lights (or use recirc).
 

Underdawg

Thread starter
Messages
15
Location
New England
Originally Posted by Fraser434
Do you have any oil loss between oil changes? I would do a cylinder leakage test to see if you have a bad cylinder. Sounds like you need to change the catalytic converter, I wouldn't recommend changing a low ash oil ACEA C1,C2,C3, it's really splitting hairs, those oils tend to have higher engine wear, it's a two fold issue. Do you want to replace your catalytic converter or do you want replace your engine?
If a low ash oil would get me 30k out of the CAT I would roll my dice on the engine. The Prius burns 3 quarts of oil every 6,000 miles. I don't drive over 70mph.
 

Underdawg

Thread starter
Messages
15
Location
New England
Originally Posted by supton
My Camry can get exhaust fumes inside the car and I'm not sure how--I haven't found any leak. For a while it smelled like untreated exhaust; last few times more like burned oil. No idea what is causing it, but when it is acting up I just turn off HVAC at lights (or use recirc).
Supton, I do the same with the HVAC (be very aware (CO has no odor) and also don't let other people drive the car). If you are feeling brave try a can of CataClean and see if the smell goes away. It did for me (for a few days).
 
Messages
219
Location
Chicago
Originally Posted by Underdawg
Originally Posted by Fraser434
Do you have any oil loss between oil changes? I would do a cylinder leakage test to see if you have a bad cylinder. Sounds like you need to change the catalytic converter, I wouldn't recommend changing a low ash oil ACEA C1,C2,C3, it's really splitting hairs, those oils tend to have higher engine wear, it's a two fold issue. Do you want to replace your catalytic converter or do you want replace your engine?
If a low ash oil would get me 30k out of the CAT I would roll my dice on the engine. The Prius burns 3 quarts of oil every 6,000 miles. I don't drive over 70mph.
You have an oil consumption problem, that's causing a catalytic converter problem. Not an oil problem.
 
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17,716
Location
NH
Originally Posted by Underdawg
Originally Posted by supton
My Camry can get exhaust fumes inside the car and I'm not sure how--I haven't found any leak. For a while it smelled like untreated exhaust; last few times more like burned oil. No idea what is causing it, but when it is acting up I just turn off HVAC at lights (or use recirc).
Supton, I do the same with the HVAC (be very aware (CO has no odor) and also don't let other people drive the car). If you are feeling brave try a can of CataClean and see if the smell goes away. It did for me (for a few days).
All the more reason to not use it, if you ask me--I'd rather smell burning oil than (not) smell CO. * I'm not sure that a quart per 2k is all that much. Most OEM's won't bat an eye until a quart per 1k. Granted, this is a small engine that is running what, half of the time? The cat may well be bad due to the codes being thrown but I'm not sure if it's due to oil burning--Saturns and early 1ZZ-FE's burned oil at worse rates yet seemed to march on all the same. IMO, and it's just that, the cat may have died earlier due to oil usage, but it may well have just died because it could. I'd probably go find a spark plug anti-fouler and see what that does, if I only needed another 30k... but I didn't say that out loud.
 

Underdawg

Thread starter
Messages
15
Location
New England
Originally Posted by ka9mnx
Originally Posted by BMWTurboDzl
Sounds like the engine is worn out due to excessive blow-by.
Yes and at 260,00 miles the cat was already toast.
This feels like an intervention. Are my friends gathering here together to confront me with the reality that this car is at an end (something I have not accepted)? Interventions are supposed to include emotional support and a path forward. Is this how it ends? No closure? I think I needed to hear this (thanks). When the diesel rabbit died VW sent me a heartfelt letter congratulating me.
 
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Messages
5,509
Location
Atlanta,GA
Originally Posted by Underdawg
Originally Posted by ka9mnx
Originally Posted by BMWTurboDzl
Sounds like the engine is worn out due to excessive blow-by.
Yes and at 260,00 miles the cat was already toast.
This feels like an intervention. Are my friends gathering here together to confront me with the reality that this car is at an end (something I have not accepted)? Interventions are supposed to include emotional support and a path forward. Is this how it ends? No closure? I think I needed to hear this (thanks). When the diesel rabbit died VW sent me a heartfelt letter congratulating me.
Have a cookie and send her off via the vast dark space known as Craigslist. crush
 
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