Unexpected Catalytic Converter Replacement

Maintenance/Repairs
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21

I certainly disagree with the statement that good synthetic should not be used for more distance than straight dino. OP has the lab test done, and assuming it reports contamination and motor protection is still there, no harm is being done by running the oil that long. This is apparently mostly highway driving.

I had the lab test done on my 2002 Sienna several years ago, using Mobil-1 Extended performance oil, at 8800 miles. It still was good oil, and mathematically it would have run that same distance as OP runs his. As extra insurance, I change at around 8000 or so.

If OP did not have the lab test done, my view would be different.

Sometimes old, obsolete ideas are hard to change.

Here in Mexico, old ideas that still dominate are that cars need 20W-50. A new automotive store just opened in my mountain village and they have no oil but 20W-50. Except a few containers of straight 50.

As best as I can tell, old, obsolete ideas also reign here. I went looking for 10W-30 several years ago, and the young dude in the oil shop snarled, “That will ruin your motor!”

It is bad, of course but the same wrong principle that good synthetic with a lab test can’t be run any longer than straight dino.

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@irlands … I don’t use synthetic so have no personal experience with it. But here’s where I read the recommendation that mileage between changes shouldn’t be extended when using synthetics.

“Extending change intervals [when using synthetic oil] are false economy. In my opinion, using conventional oil and changing more often is a far better plan.”

http://www.agcoauto.com/content/news/p2_articleid/122

OP … as noted above “direct fit” isn’t the same thing as “OEM”. That is probably why the replacement cat didn’t last as long. It just didn’t have the same quality as the OEM part. OEM parts are – or at least supposed to be – the same as what came original to the car. Most likely your earlier-than-expected cat failure isn’t engine related.

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Thanks to everyone for your feedback!

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The price for either the aftermarket or OEM is outrageous. They must be replacing the entire mid pipe. My suggestion is to have them hack out the bad cat if that is the case, and weld in an aftermarket one, which should be about $100 + labor.

Also the 11-12k oil change makes me cringe! But hey, you’re knocking on 200k so it seems to be alright.

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George, for many years on this board, I read every imaginable personal opinion on oil type and oil changes. And, everyone who stated a personal opinion always had a reason for that personal opinion. And, every reason for a personal opinion was actually just a personal guess as to what was appropriate to do.

So much so that it is probably a waste of time to even ask here which type of oil to use, and how long to go between changes.

There were even always the usual suspects who to this day insist if you really care for your car, you will change that oil every 3,000 miles. Without regard to much improved oils since we stopped living in caves. [/sarcasm]

I got tired of that random decision making process, and chose to change my Mobil-1 EP at 8800 miles and send it out for test.

Blackstone does a really good job of testing. They test for overall oil condition; and acid protection, I think you call it, and test for every sort of contamination.

They can tell you if your oil is contaminated by coolant; dust from air filter leaks; combustion by-products; bearing or other engine wear; and probably other stuff I have forgotten.

And, they let you know if your oil condition is within usable ranges on every parameter.

My oil at 8800 miles had a lot of use left in it, in every characteristic. Mathematically, it looked as if it would be good to 11,000 miles, though I have chosen to replace at around 8,000 miles or one year of driving in Mexico if less than 8,000 miles.

How many of you would go 8,800 miles with dino oil? Volunteers?

Now, let us look at that link you supplied. Another personal opinion apparently based on guessing. He says, wal, goshie darn, all oil gets contaminated, and synthetic gets contaminated at the same rate as regular oil. So, better to use regular dino and change it more often.

Oh, really? That is based on the false premise that contamination is a killer on synthetic oil. (At this point, I am not even sure contamination is the killer on dino oil. It may be, but I don’t have data to show that.) Based not on someone’s guess, but my own oil test, I am sure contamination is not a killer for synthetic oil on a good motor in long distance driving. So, he is bringing up a straw man and then making a recommendation based on that.

Not that I mind people making their decisions on oil usage and changes, based on guessing. I am enough of a libertarian I wouldn’t have it any other way. The problem is when that personal opinion rises to the level of a recommendation for people who are trying to learn! So, tell us why and when you change your oil and which type you use. Readers can look through the wild guesses and pick one that suits them, or that they want to try.

But, recommendations of any real value can only come from the true experts, who happen to be the lab that tests your oil. Or, of course, the engineers who designed the car in the first place, which usually means change it a lot less than most people here do.

Interestingly, he actually agrees with the various advantages of synthetic oil for all motors, then based on the straw man of contamination recommends against the obvious correct choice.

I have noticed that many newer cars are now recommending synthetic oil. Their usual reason is the new motors work to different tolerances. Maybe so; maybe not. I must wonder if that recommendation is also based on an attempt to avoid early breakdown when people don’t change their oil often enough. Just in case.

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Fender. my ‘opinions’ are based on Blackstone oil testing. Nothing to cringe about at all.

But, it only applies, IMO, on my Toyota Sienna with good motor, and long distance driving outside the snow zone. Different driving cycles, a person should test on his motor and his driving cycle.

A really strange one that I have mentioned before. Here in Mexico, based on the same wild guessing principles normally linked to oil type selection and change parameters, here in Mexico, most people believe you MUST use 20W-50 oil on ordinary cars.

A new oil store just opened up, right where i normally park when I am going down town. They don’t even stock anything but 20W-50 or straight 50. AutoZone in Tehuacan likewise once had nothing else in stock.

A year or two ago, I was looking for Quaker State 10W-30, when I started my abortive attempt to test dino oil at 5,000 miles to see the difference. I went into one of the small oil stores, and when I asked for 10W-30, the punk on the other side of the counter SNARLED at me, “That will ruin your motor!”

I don’t know when that nonsense got started, but I guarantee you it was not started by oil experts, nor car experts. My guess is, it was started by wild guessing, passed down through the generations. A real cultural peculiarity.

Last year, an x-ray machine owner told me, “You see our motors aren’t as good as your motors. Mexico sends you the good motors, and we only get the bad ones.”

No, they are good motors, until they are driven around full throttle with 20W-50 in them, heh, heh.

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The conventional wisdom seems to be that heavier oil will be okay under heavy loads, etc. However, I have read some articles which state that some complicated valve systems require light oil to stated viscosity spec to work properly. I know nothing much about that, but it is an interesting statement.

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Not trying to bad talk your choice to change every 12k miles.

It still makes me cringe regardless. Changing viscosity is a bad idea certainly, however I still feel its important to change fluids often. For oil thats anywhere from 3-5k depending on what driving conditions are happening. I do know that when I pulled my oil pan on my 1998 200k mustang, the crank case looked new inside.

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"Extending change intervals [when using synthetic oil] are false economy. In my opinion, using conventional oil and changing more often is a far better plan."

This coming from a shop that makes more money, the more oil changes they do. Not surprising at all.

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There is synthetic oil and there is synthetic oil! Irlandes usues EXTENDED DRAIN Mobil1, which has a lot more additives in it than other synthetics. This additional package allows him to go safely to 8000+ miles between changes.

Manufacturers will not make any exception to the drain intervals stated in their manuals.

Truck fleet managers do routine oil sampling to optimize the drain interval and to check if anything is going wrong with the engine.

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Honestly, i never got the allure of synthetic. It makes my engine run slightly noisier and it costs much more. Kind of a wash there if you drive it much longer. More frequent changes at less cost is cheap engine life insurance in my book. And i have a clean high mileage engine. But to each their own.