Q: Rotating your tires is a scam by the auto manufacturers, tire companies and auto dealers. If tires cost $125 each, replace one. At the most, just replace the two front tires and later the two rear ones. If you rotate, they all wear out at once, costing you $500. The extra tread on one tire will not affect steering, braking or anything else. I am in my 80s and have never replaced more than one tire at a time. Give people the honest story.
— J.J., Bloomfield, Conn.
A: There was a time, long ago, when you may have been right. But today's vehicles are very sophisticated and uneven wheel rotational speeds, which can vary if one wheel's diameter differs from the rest, can affect such things as anti-lock brakes and automatic stability control. Rotating your tires, as you infer, makes them all wear evenly.
Q: I got an oil change recently at a tire shop and the manager told me there was a nail in the sidewall of one of my tires and that it could not be repaired. He then said that I needed to buy four new tires since my Honda is all-wheel-drive. I am not too upset since my original tires are almost due for replacement, but do you think they were trying to scam me?
— T.Q., Bluemont, Va.
A: No, they were not trying to scam you. Replacing just one tire not only affects the things we mentioned in the previous answer, but the difference in diameters continuously activates the viscous coupling for the AWD causing it to overheat and fail. You may end paying more than the cost of a couple sets of tires to replace the coupling.
Q: Good piece last week on new turbo applications. Since my first ride 45 years ago in a very tweaked turbo Corvair that humbled Mustangs of the era, I've been impressed by the turbo's potential. The critical modification which kept the pistons, heads, valves, etc. from melting under the higher boost temps was a primitive adaption of the Olds Jetfire "Rocket Fluid" alcohol water injection system and, I think, a four barrel carb setup. My question is with today's high-tech precision direct injection, engine control systems, and cheap E-85, why isn't the cooling injection and the power benefits part of the current picture?
— J.S., Elgin, Ill.
A: The simple answer is that it would affect the catalytic converter. If you boil it down, current engine controls are designed to keep the cat content so it can do its job of eliminating exhaust emissions. Currently, the most common way to keep intake air charge temperatures within reason is to install an intercooler (a heat exchanger) between to turbo and intake.
Q: I need confirmation that I'm doing this right. My 2000 Honda Accord and older Corvette do not get driven much. The Honda is driven less than 2,000 miles per year now, and the Corvette is driven less than 300 miles per year. Obviously, neither comes close to the old "3,000 miles or every 3 months" when it comes to oil changes. I change the oil in the Honda twice per year, and in the Corvette once per year (using Mobil1 — the only oil I use in any of my cars). This seems to be sufficient, but I'm wondering when the "3 month clock" starts on oil? I'm concerned that driving either car, then not even starting it again for several months may indicate a need for oil changes based on time.
— J.H., Chicago
A: It seems wasteful to change the oil every time you drive your car, which we guess is how you use them. For instance, you may take the Vette out a couple times during the summer then put it away. As such, you can simply change the oil prior to storage and it will be fine. The oil clock starts when you start the engine. Your routine has now been confirmed.
Q: Your August 26, 2012 article on plastic starter gears could have included information on preventing the problems. If someone in the family is activating the starter while the engine is running, goodbye starter gear. On a false start, double pressing the starter before the engine or starter have stopped stop spinning will also grind the plastic starter gear to shreds.
— H.R. Highland Park, Ill.
A: Yes it will, and does pretty much the same with metal gears after a few times. We cringe every time we hear someone hit the starter on a running engine. To us, it's worse than fingernails on a blackboard.
Q: I have a 2011 Honda Accord with 23,000 miles. Went to the dealer for an oil change and received their usual Recommended Services report. Under Inspection Recommendation I found "Perform automatic transmission drain and fill (Found automatic transmission fluid to be contaminated/dark - $112)." I have never heard that something like this is needed at 23,000 miles. Is the dealer trying to rip customers off pushing uneeded service? If the fluid is really contaminated shouldn't this be a part a warranty service?
— N.G., Simsbury, Conn.
A: Yes, the service advisor is trying to pad the bill and make some money for the department. Although most owner's manuals have no schedule for automatic transmission fluid changes, we still do it on our vehicles. It is a good preventive measure. But we only do so about every 50,000 or 60,000 miles. The color of the fluid is no longer a reliable indicator of its health. Fluids do not qualify for warranty replacement.
Q: Some time ago, the window for the gear selection on the instrument panel on my 2003 Buick Century quit lighting up. Everything else lights up fine. No one seems to know how to repair it. I am tired of shifting by Braille. Can you help?
— M.W., Pembrook Pines, Fla.
A: The I.P. on your car has several small lamps — light bulbs — and one may be burned out. The lamp itself is cheap and simple to replace, but getting to it requires removing the instrument cluster from the dash. Since there may be issues with the airbags, we suggest leaving this task to a qualified professional.