Liqui moly ceratec O2 sensor

[Henmen]

Would using the ceratec additive be harmful to O2 sensor and Cat if my Subaru is burning a little oil? (About 0.3qt/1000 miles)
About 1.5k miles after I used this additive with my oil change I am getting a p0420 code. Only other change is a k&n air filter. I ordered new O2 sensors which it probably needs anyways 263k miles. Just to be safe should I do an oil change before replacing the O2 sensors?
Thanks

 

[demarpaint]

The Ceratec additive might be harmful to the 02 sensor and Cat if you're using oil, although you aren't using that much oil. Honestly I'd be more concerned with the K&N air filter. They increase air flow at a cost. The cost is poorer air filtration, which can allow harmful junk to enter your engine via the air intake system. Flame suit on. There's a lot of info here, and on the web regarding K&N air filters, with UOA data backing up my statement. I wouldn't use one, or Ceratec for that matter.

 

[blufeb95]

I'm gonna say the 263,000mi has more to do with failure of the cat and/or O2 sensors rather than a recent oil change using ceratec.

 

[Henmen]

I'm gonna say the 263,000mi has more to do with failure of the cat and/or O2 sensors rather than a recent oil change using ceratec.

Yes definitely the mileage is not helping. It has the head gasket replaced in the life before I bought it so I know just that could mess up the O2 sensors. Luckily power is not bad and good mpg so hoping the cat is ok.
Will probably go back to a standard filter just liked the one and done aspect and wanted to see if I got better mpg.

 

[kschachn]

Will probably go back to a standard filter just liked the one and done aspect and wanted to see if I got better mpg.

One would never be able to correlate an observed MPG change to an air filter in everyday driving. Not even close.

 

[Henmen]

One would never be able to correlate an observed MPG change to an air filter in everyday driving. Not even close.

Yea just the super long change intervals like 50k would be cool. So just get a higher end paper like wix or try to get oem?

 

[TiGeo]

263K miles - I'm pretty sure these two things aren't related at all.

 

[TiGeo]

The Ceratec additive might be harmful to the 02 sensor and Cat if you're using oil, although you aren't using that much oil. Honestly I'd be more concerned with the K&N air filter. They increase air flow at a cost. The cost is poorer air filtration, which can allow harmful junk to enter your engine via the air intake system. Flame suit on. There's a lot of info here, and on the web regarding K&N air filters, with UOA data backing up my statement. I wouldn't use one, or Ceratec for that matter.

None of my many UOAs from multiple cars running K&Ns show any hint of filtration issues.

 

[demarpaint]

None of my many UOAs from multiple cars running K&Ns show any hint of filtration issues.

I'm glad to hear it, maybe where you live has something to do with it. There are plenty of UOAs showing otherwise. Plenty of better air filter choices imo too.

 

[blufeb95]

I'm glad to hear it, maybe where you live has something to do with it. There are plenty of UOAs showing otherwise. Plenty of better air filter choices imo too.

I don't get the point they're expensive up front, the only way you're supposed to clean them is with their special cleaning kit, it really needs to dry after you clean it, so you either have to leave the filter out for several hours or buy two, I don't see how it's any less expensive or anymore convenient than a disposable.

 

[TiGeo]

I'm glad to hear it, maybe where you live has something to do with it. There are plenty of UOAs showing otherwise. Plenty of better air filter choices imo too.

My point is that in these convos re K&Ns - it's always taken as a fact that the filters cause bad UOAs - it's not the case and YRMV is the word of the day. You want to run one? Try it and do a UOA before and after and see. You aren't going to blow up your car here. If you are in a higher-power application, more flow is typically a good thing.

 

[TiGeo]

I don't get the point they're expensive up front, the only way you're supposed to clean them is with their special cleaning kit, it really needs to dry after you clean it, so you either have to leave the filter out for several hours or buy two, I don't see how it's any less expensive or anymore convenient than a disposable.

A K&N drop-in is ~$50 for most vehicles I've bought them for. The cleaning/oil kit is $15 and should last a "lifetime" - the cleaner is just the typical purple degreaser you can find at Walmart so nothing fancy. $65 for a lifetime filter. Pretty easy math to compare against disposables for a vehicle that is kept 5-10 years. Hassle factor is a separate issue and everyone values their time and hassle differently. The filters should be cleaned at ~50K miles per K&N and that has proved out in my area in the mid-Atlantic. I'm sure you clean them more out west/dustier conditions. In my Golf, you have to do it more freqently b/c the filter is on an open-element intake. For that car, I have 2 filters for quick swaps. On the others, I do it over night. You can also just keep the OE filter and drop that in when you do this which is really the best/easiest method.

 

[Trav]

Would using the ceratec additive be harmful to O2 sensor and Cat if my Subaru is burning a little oil? (About 0.3qt/1000 miles)
About 1.5k miles after I used this additive with my oil change I am getting a p0420 code. Only other change is a k&n air filter. I ordered new O2 sensors which it probably needs anyways 263k miles. Just to be safe should I do an oil change before replacing the O2 sensors?
Thanks

More than likely at that mileage the cat has had it. You can probably get a Eastern cat for it (you didn't post year or model) that will work fine and it is good practice to replace the O2's at the same time anyway so no loss.
Ditch the K&N and use a quality paper filter like Wix/Napa gold, use a OE quality oil filter and good oil changed often and stay away from the snake oils. Your engine will keep going just fine.

 

[demarpaint]

My point is that in these convos re K&Ns - it's always taken as a fact that the filters cause bad UOAs - it's not the case and YRMV is the word of the day. You want to run one? Try it and do a UOA before and after and see. You aren't going to blow up your car here. If you are in a higher-power application, more flow is typically a good thing.

No need for me to try one, I bought into the hype years ago, and ditched the filter. I saw enough data to steer me away, sadly after I used one for a while. You're happy with them, that's all that matters, people considering them should do their homework and decide for themselves. People who live in desert climates, or areas where wind driven sand etc. is blown around are asking for trouble. YRMV............

 

[demarpaint]

I don't get the point they're expensive up front, the only way you're supposed to clean them is with their special cleaning kit, it really needs to dry after you clean it, so you either have to leave the filter out for several hours or buy two, I don't see how it's any less expensive or anymore convenient than a disposable.

I saw zero value, and more negatives than positives, for me. In the garbage it went.