Toyota-Lexus-Subaru-Honda Catalytic Converter

Catalytic Converter Our experience is that the Toyota catalytic converters are clearly and significantly superior to the aftermarket catalytic converters. They clean up the emissions much more aggressively right out of the box, and they typically last from five to ten times as long.

The brand new aftermarket cats we’ve had occasion to test have passed the emissions test by the thinnest of margins, where a Toyota catalytic converter would have easily passed with room to spare.

The Toyota cats run much cleaner on sudden accelerations as well. We’ve tested the emissions of Toyotas with brand new Toyota catalytic converters on repeated back-to-back snap accelerations (which lends itself to creating maximum emissions) and the result has been that we see a high of only 50 or 60 parts per million of unburned hydrocarbons (HC). Doing the same test on brand new aftermarket cats has resulted in hydrocarbon readings as high as 1700 to 2000 parts per million.

As for longevity, over and over we’ve seen people who have replaced their cats with aftermarket cats get stuck in a cycle where from then on they have to replace the catalytic converter every two years just to make it through DEQ. A further problem with aftermarket cats is that in order to install the “universal” cat, the muffler shop will cut a section out of the original piping in order to weld in the non-Toyota cat. At that point, if the owner ever gets frustrated with having to replace the cat over and over and wants to return to a Toyota cat, he has to spend even more than he would have, because he now has to replace the piping on either side of the catalytic converter in order to restore the bolt-up flanges that have been cut off.
We were recently discussing cat costs with a Tundra owner and had occasion to calculate the cost per mile of one of Toyota’s most expensive catalytic converters. In this instance, the cost worked out to about 1 ¾ cents per mile. It had lasted 150,000 miles. Models with less expensive cats commonly work out to less than half a cent per mile.

If the aftermarket cat this person was considering were to fail within a year-which is not uncommon-then it would cost about 5 cents per mile if it lasted 15,000 miles. That’s approaching 3 times the cost per mile. (Okay, okay, it’s 2.857 times the cost per mile.)

While going over this with the customer, she mentioned that a muffler shop had told her that they were using an OEM part that would be the same as the Toyota part because supposedly OEM meant that it was made by the original manufacturer for Toyota. What OEM or Original Equipment Manufacturer actually means is that this company at some time has supplied some sort of part for Toyota-could be anything, could be a gasket. What it doesn’t mean is that they provided the catalytic converters. If they had provided the cats, they certainly wouldn’t be trying to sell generic cats that required cutting the old ones out and welding the new ones in.

As far as Catalytic converter failures go, they can fail in a number of ways and from a number of causes. Most commonly, their ability to clean up emissions eventually simply fades out and they either fail the DEQ emissions test, or, for newer vehicles that monitor the converters, the computer can turn on the check engine light and will set a code that says “catalyst efficiency below threshold.” If your engine is chronically burning oil, it tends to leave crusty deposits on the cat and make it effectively inert. If those deposits continue long enough, eventually it plugs up the cat and you experience a severe loss of power, because the exhaust can exit quickly enough to allow the engine to take in the quantities of air it needs for power. Driving the car with a cylinder misfiring causes the cat to overheat as it ignites all the unburned gasoline to burn in the cat itself. In this case, it can run so hot that the catalytic converter material disintegrates. This can lead to chunks of material getting lodged in the exhaust system in a manner that plugs up the exhaust and causes severe loss of power. Another way in which the catalytic material can be broken up is if something strikes the outside of the cat hard enough.