Q I own a 2004 Explorer (you helped me once before) that I purchased shortly after the Firestone/rollover fiasco. It didn't take me long to feel comfortable with the handling of my Michelin X-Terrain tires. I have a tendency to enjoy the back roads — enough said. Now that I'm retired and look at some expenses as "what percent of my Social Security check is this going to be?" I'd like to move on to some less expensive tires. My rear tires are in excellent shape, but I do need two front tires. I've been told by dealers of Michelins that I can't mix tires because of the four-wheel drive. It seems illogical to me that if I have 235/70R/16s and get the same-size tire with similar tire pattern and depth that it would have any adverse effect. Is this just a marketing tool or is there some validity to it?
A A tire of a similar tread pattern that is within 20 percent of the circumference of the old tires should work just fine. What is important, however, is that the similar tires are on the same axle. By that, I mean both Michelins on the front or on the rear, and of course the same with the new tires.
Q Recently, I requested a tuneup on my 2006 Lincoln Mark LT pickup truck with 100,000 miles on it. When I arrived to pick up my truck, the mechanic said he did everything but change the plugs. When I asked why, he stated that they are too difficult to remove without breaking and could require removing the heads to get them free. This would be an extremely costly tuneup. I know the aluminum heads may make it difficult to extract the plugs, but can it be done in a prudent and cautious manner to minimize breaking? (Maybe using Marvel Mystery Oil or Break-Free?)
A This is a problem. The spark plugs at 100,000 miles lock themselves into the aluminum cylinder heads. However, the manner you speak of is the best way to do the job. That being said, I have had them break on me, too. Because this is such a common problem, tool manufacturers make tools for extracting the broken plug and seldom does the cylinder head have to come off. For the record, I applaud the mechanic that knew this job was going to be over his head, rather than to start and not be able to finish the job due to either lack of equipment of lack of experience.
Larry Rubenstein is a master technician who owns a North Shore service station. Write to Larry by email to email@example.com.