Q: Everything was fine with my 2010 Chevrolet Equinox until March 2014. It quit running and the warning light indicated to change oil. I took it to three dealers and they could find nothing wrong via the computer diagnostic system. I took it to an independent; he said the timing chain is the problem. I took it to another Chevy dealer and they could find nothing wrong. I told them what the independent dealer said about the chain. They looked at it again and determined there were bits of metal and plastic in the oil pan. The pistons had been seared. The repairs were covered under warranty. If the computer does not report problems, who diagnoses mechanical problems?
— N.B., Naperville, Ill.
A: We are afraid that some technicians have lost the art of using their eyes, ears and nose to detect problems. Instead, they defer to an electronic device that is not designed to find mechanical faults. It sounds like you have a good independent technician. Stick with him. He uses the best computer in the world: His brain.
Q: I purchased a 2011 Subaru Forester last September in a sky blue color. Since then, I have noticed lots of black dots across the front of the car, which do not come off when I wash it, even if I scrub. That makes me think it must be tar from the highway or tiny pebbles that are imbedding into the surface. I do quite a bit of highway and city driving. Do you know of any way to get rid of these? Other than that, the car looks sparkling and new.
— J.V., West Hartford, Conn.
A: It could be particulate matter from sand to industrial fallout or anything in between. A professional detailer can usually sort it out. He will probably use a clay bar to remove the specks. Once you see how this is done, you can probably do it yourself.
Q: My village didn't inform us that they were glazing our street this morning. So I had to drive over the fresh stuff to get to work and it's now on the sides of my car and my rims. The civil engineer told me it was a water-based sealer that they put on top of the black top to make it last longer. A friend suggested WD-40. I bought some Goo Gone and that seemed to work on a patch. Do you have any advice on the best way to remove this?
— S.P., Oak Park, Ill.
A: The stuff sounds a lot like driveway sealer. Sealer and most road tar can be easily removed with tar and bug remover available at most auto parts and big box variety stores. But since you have been told that it is water based, try a soap-based product. We have heard of using mayonnaise, but don't much care for it, even on a sandwich. Whatever you use, start with the least aggressive stuff first. Afterwards, apply a good coat of wax.
Q: According to (a recent column), M.N.'s '04 Ford Escape is leaking 9 to 13 quarts of oil onto the streets of Joliet. Most of this probably ends up polluting the DesPlaines River, then the Illinois River. If every car on the road did that, the DesPlaines might catch on fire like the Cuyahoga did in Cleveland in 1952. Tell him to give a mechanic some work, get the leak fixed, and help improve water quality in our streams and rivers.
— M.H., Joliet, Ill.
A: All right, already. We will pass that along. But ponder this: Where does the rubber go as tires wear?