Viewer-submitted questions for The Car Doctor:

Q. I have a 2019 Acura MDX with 25,000 miles. There is no printed service interval for this SUV; dashboard codes light up when service is needed. I went to the dealer for a state inspection today, and they recommended several services, even though no codes appeared. They suggested I replace the cabin and engine filters (even though I replaced them 14k miles ago), transmission service, oil change, front and rear differential fluid service, and emission service. I declined them all, but am wondering if I should have proceeded? If so, then what is the point of the codes on the dashboard?

A. There are certain times that the Maintenance Minder can be ignored since service is based on time or mileage. For example, if the oil change reminder doesn’t come on after one year, you should still change the engine oil. As far as some of the other services, Acura states “Driving in mountainous areas at very low vehicle speeds or trailer towing results in higher level of mechanical (Shear) stress to fluid. This requires differential fluid changes more frequently than recommended by the Maintenance Minder. If you regularly drive your vehicle under these conditions, have the differential fluid changed at 7,500 miles (12,000 km), then every 15,000 miles (24,000 km).” The transmission fluid has roughly the same recommendation. But, unless your driving fits this severe category, I would watch the Maintenance Minder and look for codes 4 and 6 to indicate those fluids need changing. The idea of these electronic systems is to reduce over-maintaining your vehicle, save money and reduce waste. Over-maintaining a vehicle is not terrible, but it’s not necessarily in the best interest of the consumer.

Q. I recently picked up a road hazard in a rear tire on my Ford Edge SUV which is causing a slow leak (3-4 psi in 24 hours or so). I found the item in the sidewall very close to the tread belt area and removed it. It left a tiny puncture hole that is almost invisible to the eye (slightly bigger than a needle would make perhaps). Is it necessary for me to discard the tire – a Michelin Latitude Tour HP – with just 16,000 miles of treadwear? I realize that repair or patching is not usually advisable, and some suggest replacing two tires and not just the damaged one. I have been driving on this tire for about a month and simply re-inflating it every couple of days. Is the risk of a blowout too much under the circumstance?

A. There was a time when Michelin said a minor puncture could be patched from bead to bead, but over the years they’ve moved to only recommending repairs in the tread area. As for driving with it, the tire could become under-inflated while driving, causing the sidewall to heat up and cause a blowout. Another issue to consider is that the longer you wait, the punctured tire will experience more tread wear. Eventually, you’ll have to replace two or possibly four tires so they all match correctly. The best practice is to replace the tire. Another option – depending on tread wear—is to purchase one tire and have it shaved down to match the current tread depth of the other tires.

Q. Some years back I owned a 2005 Land Rover Freelander. Eventually it blew a head gasket (luckily before warranty expiration). When researching online it seems the major flaw was in the engine cooling system. Do you know what the specific issue was? It was never explained to me in detail. It was kind of a shame; it was a fun vehicle when it ran.

A. The engine itself was extremely sensitive to overheating damage from any coolant loss or even failure to maintain coolant levels. When this engine overheats, it can lead to head gasket failure. Although this is typical of most engines, this 2.5-liter engine was particularly sensitive to overheating. I remember talking to an engineer about this and he felt it was a design issue and there were not enough head bolts to secure the cylinder head to the engine block. The repair involved a new head gasket design, new head bolts and, in some cases, a new cylinder head. Occasionally, when the engine overheated, the piston rings would seize to the pistons and require complete engine replacement. You were lucky the vehicle was under warranty.

Q. I own a 2019 Buick Envision that originally came with Michelin tires. A few months ago, I needed to replace the tires, but the same Michelin’s were no longer available. My mechanic (who I’ve known for years) recommended Uniroyal Tiger Paw tires, saying he had them on his personal vehicle. Ever since I purchased them, I feel a bad vibration on the front-end right side when going over a depressed manhole or a bump in the road. It does not happen all the time, but it is frequent. I brought the SUV to the dealer to be checked and, after paying more than $250, they could not find anything wrong and determined the SUV was safe. I brought the vehicle back to my mechanic and he couldn’t find the problem either. Yet, when I hit a bump in the road it vibrates and the front-end shakes. Could the tires be at fault? Are they a harder riding tire? Another thought I had is the traction control is not working right with the change of tires. The size of the tires is correct. Do you have any ideas of what it could be? Have you ever heard of this happening before?

A. I don’t believe the issue has to do with the tires. The common issue is the front control arm bushing needs replacement—usually the rear-front control arm bushing. It is an oil-filled bushing and usually you will see a bit of oil staining on the bushing. This was a common enough problem that Buick put out a Technical Service Bulletin on the subject. Have your repair shop or the dealer look at #PIT5998: Diagnostic Tip- Steering Wheel Shake After Hitting Bump(s).

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