Did 1qt tot 2000mile oil consumption kill my catalytic converters after 230k miles?

Messages
186
Location
The Netherlands
My bmw n52 engine 2.5 inline 6 recently gives fault codes on both cats below efficiency. 1 cat per 3 cylinders.

I can clear the codes but after a couple of miles the codes come back, strangley the always come simultainsly on both cats.

If i clear the codes, let the car sit for the night they are away for like 10 miles. But then they re appear again, like the ecu is doing some kind of check then after warm up. This is only when i drive like 60mph. If i head in to town they will stay away longer.

I have changed the pre cat lambdas because officaly their service life is only 150k miles but this didnt help.

I wont spend a ton of money on this because emmisions are fine and it runs like it should.

Milage is now 230k miles with oil consumption of around 1qt per 2000 miles.

Car is driven hard for long distances, a lot of 120 mph highway runs.

Car has always been filled on ll04 spec oil for all its life.

The last 80k miles where on shell helix am-l 5w30.


Could oil have killed my catalysts or is there something else going on. I have read up on clogged catalysts but then you would also lose power.

As i said the car is driven hard so you would assume this would be burned out all the time.

Does anybody have experience on this?
 
Messages
1,252
Location
NC
My bmw n52 engine 2.5 inline 6 recently gives fault codes on both cats below efficiency. 1 cat per 3 cylinders.

I can clear the codes but after a couple of miles the codes come back, strangley the always come simultainsly on both cats.

If i clear the codes, let the car sit for the night they are away for like 10 miles. But then they re appear again, like the ecu is doing some kind of check then after warm up. This is only when i drive like 60mph. If i head in to town they will stay away longer.

I have changed the pre cat lambdas because officaly their service life is only 150k miles but this didnt help.

I wont spend a ton of money on this because emmisions are fine and it runs like it should.

Milage is now 230k miles with oil consumption of around 1qt per 2000 miles.

Car is driven hard for long distances, a lot of 120 mph highway runs.

Car has always been filled on ll04 spec oil for all its life.

The last 80k miles where on shell helix am-l 5w30.


Could oil have killed my catalysts or is there something else going on. I have read up on clogged catalysts but then you would also lose power.

As i said the car is driven hard so you would assume this would be burned out all the time.

Does anybody have experience on this?
Don't know if the oil did it, but 230k miles combined with cat melting 120mph runs definitely could have.
 
Messages
5,369
Location
down in the park
My bmw n52 engine 2.5 inline 6 recently gives fault codes on both cats below efficiency. 1 cat per 3 cylinders.

I can clear the codes but after a couple of miles the codes come back, strangley the always come simultainsly on both cats.

If i clear the codes, let the car sit for the night they are away for like 10 miles. But then they re appear again, like the ecu is doing some kind of check then after warm up. This is only when i drive like 60mph. If i head in to town they will stay away longer.

I have changed the pre cat lambdas because officaly their service life is only 150k miles but this didnt help.

I wont spend a ton of money on this because emmisions are fine and it runs like it should.

Milage is now 230k miles with oil consumption of around 1qt per 2000 miles.

Car is driven hard for long distances, a lot of 120 mph highway runs.

Car has always been filled on ll04 spec oil for all its life.

The last 80k miles where on shell helix am-l 5w30.


Could oil have killed my catalysts or is there something else going on. I have read up on clogged catalysts but then you would also lose power.

As i said the car is driven hard so you would assume this would be burned out all the time.

Does anybody have experience on this?

Don't forget it's the after cat lambda sensors that are reporting this. Monitor their voltage. They are subject to the same aging as the pre cat lambdas. After the cat there should be no oxygen in the exhaust so the after cat lambdas read rich unless you are coasting down. But they need to get sufficiently hot to do this. If you run harder and the faults stay away longer definitely look into the lambdas. One or both could be at fault.
 
Messages
5,148
Location
Ohio
1 quart per 2000 miles isn't that terrible and some car makers say that's normal. I would guess a rich running engine and high miles are factors with your CAT failing. I had an old Dodge that used a quart per 500 miles and it still passed tail pipe emission tests at 175k miles. They are pretty resilent.
 

Flyingdutchman

Thread starter
Messages
186
Location
The Netherlands
Don't forget it's the after cat lambda sensors that are reporting this. Monitor their voltage. They are subject to the same aging as the pre cat lambdas. After the cat there should be no oxygen in the exhaust so the after cat lambdas read rich unless you are coasting down. But they need to get sufficiently hot to do this. If you run harder and the faults stay away longer definitely look into the lambdas. One or both could be at fault.
They swing around 0.7 volt during cruising.

In bmw inpa it turns red when they are 0.9 or higher.
If i am not mistaking with this engine the pre cat sensors are air fuel ratio sensors and the post cat where only oxygen sensors.
 
Messages
5,369
Location
down in the park
the pre cat could be wide band lambda if it's a direct injection engine with lean burn etc.. otherwise they are the same thing.

If they stay well above 0.5V and don't go crazy high (like the 0.9V) the cats and sensors are ok. they should drop below 0.4V when you coast down though
 
Messages
359
Location
VA, US
230k miles combined with cat melting 120mph runs definitely could have.
^ That!
It's amazing what expectations people have from their cars :oops:

Oxygen sensor spacers/defoulers would probably keep the cel off.
And mess up the engine further, because of running permanently in open loop.

Could oil have killed my catalysts
If it was high in Zinc and Sulfur, yes. European cars (cats) are more sensible to that, compared to the ones for US market, because different oil formulations.
Remember that hot runs are dumping rich mixtures in cylinders, because the Oxigen Sensors are in open loop for those relative short bursts of power.
 
Last edited:

Flyingdutchman

Thread starter
Messages
186
Location
The Netherlands
It's amazing what expectations people have from their cars
With our neigboughrs in germany every car imagniable sees 120mph highway runs.
These 2.5l inline six'es bmw's where made for it.

And mess up the engine further, because of running permanently in open loop.
Yeah i have been thinking about this but i wont mess with it. I am not really bothered by the code and according to dutch laws it doesnt matter if this code is stored. The car had an MOT recently and emissions where fine.

A mate of mine tried that with a decatted car but it didnt work like it should, he told me that the holes got clogged after a while.

Also cars with poorly functioning cats useally smell like rotten eggs. Mine doesnt have this at all so i am assuming that something goes wrong with the measurements/parameters.
 
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