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Is it worth replacing the catalytic converter in my 25 year old car?
John Paul, AAA Northeast's Car Doctor, hears from a reader whose 2000 Buick has a catalytic converter with a hole in it.
Q. I have a 2000 Buick LeSabre. When I took it to Buick for an inspection, they said the exhaust pipes were rusted and replaced them. They also said I had a hole in my catalytic converter but since the car was old, they couldn’t get a new one. The car passed its annual vehicle inspection. They said in order to fix it, I needed to go to an exhaust/muffler shop. I haven’t fixed it yet since it passed inspection. I was wondering if I need to replace it or is it ok to continue driving with the hole in it? I hardly drive, just local trips around town. The car is 25 yrs old, has only 68,000 miles, and runs great. As far as I know there are no other problems.
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A. If the catalytic converter actually has a hole in it, then there is a possibility of exhaust gases leaking into the car. If the hole the Buick dealer mentioned was in the internal workings of the converter, then it can’t do its job to lower exhaust pollution. If this is the case, the check engine light will be turning on at some point. Although the Buick original converter is not available, there are direct-fit aftermarket converters which range in price from $150 to $300. I certainly would get a second opinion from an independent shop to find out what is actually going on.
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Q. My lease on my 2023 Hyundai Tucson is expiring. I have decided to lease again. I’ve always owned and driven a sedan. I love my Tucson, but I’m ready to go into something smaller. Any ideas? I really enjoy reading your column every week, always good advice.
A. If you are considering a sedan, the Hyundai Elantra and Kia K4 are good small sedans. Although the Elantra and K4 are very similar, I prefer the Elantra which has a little more interior space and more standard safety features. Also the Elantra is available as a hybrid. If you are looking for a smaller SUV the Kia Seltos and Mazda CX-30 are quite good in my opinion.
Q. My daughter sold her car, and I have a few quarts of 5W-30 Mobil One oil left. My wife’s car, a 2007 Honda Odyssey uses 5W-20 oil – also Mobil 1. Can I add one quart of 5W-30 to the 5W-20 oil on future oil changes to use it up?
A. Honda, according to AllData (the technical database I use), recommends using 5W-20 oil in the 3.5-liter engine. This is for both fuel economy and emissions purposes. Mixing the 5W-20 and 5W-30 oils in such a small ratio should have very little effect on the viscosity. It is also interesting to note that in Australia Honda recommends using either 5W-20 or 5W-30 synthetic or conventional blend oils.
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Q. I was watching a video the other night, and a mechanic was using AI (artificial Intelligence) to diagnose and repair a car. What are your thoughts on this? Are you AI?
A. I used one of the AI apps to answer one of my car columns. Out of 10 questions, the AI got about five right, two more were close and with more information the answers were right and the last three answers were completely wrong. Most of these AI apps state something like answers could be wrong due to the Beta version of the program. That being said, I have seen everyone from medical to investment professionals use AI with some success. Will AI replace a good diagnostic technician? Not in the near future, but it may help with developing a repair strategy. No, I am a real person who looks up problems and does my best to understand the theory and operation of automotive systems to come up with an answer.
Q. At 72 years of age, we are interested in the 2026 Toyota Sienna AWD for occasional four- to five-hour road trips as well as daily driving. I have always bought base or mid-level vehicles, and I would like to now get a car with a quieter ride. As I climb the Sienna trim scale should I expect differences in the build that will provide a quieter ride? Do you have any perspective on the 2026 model? My second question, I am concerned with ground clearance. Should I consider getting 20-inch wheels instead of 18-inch wheels and would that affect the ride and mpg? I just don’t want to spend the extra money for the Limited trim if it does not matter in ride and noise.
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A. I have not driven the 2026 model of the Toyota Sienna but based on my impressions of the 2025 Sienna there are some differences in trim level quietness—not much and to me barely noticeable. Acoustic glass and additional soundproofing are standard on Limited and Platinum trims but not on lower-level LE and XLE trims. I would if possible, try to stay with the smaller wheel combination. The overall size is about the same, but the 20-inch tires have less sidewall, which results in a firmer ride. Also the larger diameter tires are more prone to damage from our less-than-perfect roads in the Northeast.
John Paul is AAA Northeast’s Car Doctor. He has over 40 years of experience in the automotive business and is an ASE-certified master technician. E-mail your Car Doctor question to [email protected]. Listen to the Car Doctor podcast at johnfpaul.podbean.com.
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