Q. I have a 2011 Honda CR-V that I bought new. It has 79,000 miles and runs fine. I have taken good care of it and always used high-quality gasoline. To pass inspection the upper catalytic converter and exhaust manifold needed to be replaced, at a cost of almost $4,000. I was surprised that it failed so soon. I have driven several Toyotas and other cars over 100,000 miles and never had a catalytic converter fail. Could it have been defective or is there another reason it failed so soon?

A. Normally catalytic converters are designed to last the life of the vehicle. That being said, catalytic converters can fail early from overheating, chemical contamination, poor fuel quality, weird fuel additives, alcohol, and faulty sensors. As an example, a faulty coolant sensor or oxygen sensor that causes the car to use too much fuel can overload the converter and cause it to fail. The same type of issue is if you had a spark plug misfiring it will overheat the catalytic converter. The code is most likely a PO420 and although the converter could be faulty an exhaust leak could be the cause. The price of $4000 is a little high but the shop may be adding time for rusty bolts. You may be able to save some money with a fully compliant aftermarket converter. Talk to your shop and they will know which ones work best. 

Q. I recently had an issue with my 2017 Toyota RAV4 air conditioning which stopped cooling when I turned it on. All I got was warm air and the settings were correct. I called my dealership and was told by the service representative that they would have to drain my air conditioning refrigerant and then put a dye in to see if there was a leak. The cost for that alone would be $299 and then depending on what they found, there would be an additional cost to repair it. Is this standard procedure for my issue? It just seemed like a money grab to me. After talking to my son, he suggested that I purchase a can of A/C PRO with a hose and my son showed me how to use it and we fixed the problem, and it continues to work fine. Should that have been the first step for the dealership?

A. In my opinion both options are wrong. Adding refrigerant without knowing if something else is wrong can cause an issue with overcharging. Evacuating the system without knowing if there is an electrical problem first is not a great diagnostic procedure either. In both cases some basic testing should be performed first. The good news is that that the air conditioner works, the bad news is that there is most likely a leak. The A/C PRO (a good DIY product) does have a sealer that could slow or even stop a leak. 

Q. I am an artist and recently purchased a used minivan for going to craft fairs and shows to sell my art. The good news is the family I purchased it from only used it for vacations and as a spare vehicle. The bad news is every state park or attraction they went to they put bumper stickers all over the back hatch. The paint is generally in decent shape, how do I remove the bumper stickers, without damaging the paint? 

A. Start with giving the car a good wash and then with a hair dryer or heat gun (set on low) warm up the sticker to soften the glue. When it is warm to the touch try to grab the edge of the bumper sticker and once you are able to lift it off, fold it over on itself and continue to apply heat. This is sometimes referred to as 180-degree release which works better than pulling the sticker off as a 90-degree angle. Once you remove the stickers clean up the glue with an adhesive remover such as Goo-Gone or even WD-40 can work. The adhesive remover will also remove the wax, so wash and wax the car to protect the paint. 

Q. I recently purchase a 2008 Lexus ES350 with 79,000 miles and it is in remarkable shape considering its age. The gas door states Premium 91 octane gas only. The gas stations have Regular 87 octane, Special 89 octane, and Super 93 octane gas. Which do you recommend I use?

A. According to the Lexus web site 91 octane fuel is the minimum recommended, so that would be premium -highest grade at most pumps. But it is just a recommendation not a requirement. At AAA we did some very scientific testing on vehicles that recommend premium fuel and we found in just about every case that using 87-octane fuel had no or little effect on fuel economy or performance. If you did notice a very slight reduction in fuel economy and performance, in my opinion it is not enough to justify the 75 cent’s difference in cost. Readers, if your vehicle requires premium fuel, you must use it, but if it is recommended you have a choice. 

John Paul is AAA Northeast’s Car Doctor. He has over forty years’ experience and is an ASE-certified master technician. He will answer readers’ questions each week. Email your questions to [email protected]. Follow John on Twitter @johnfpaul and friend him on Facebook at mrjohnfpaul.