Q: I have 50,000 miles on my 2010 Acura MDX with all-wheel drive and 18-inch Dunlap tires. I have been informed that one of the tires will soon require replacement and that all of the tires must be replaced at that time since the new tire will be larger in diameter than the other three worn tires. The consequence of operating the auto with unequal diameters is said to be premature wear on the suspension system. I remembered that out-of-round tires are corrected by a machine that spins and shaves rubber off the aberrant tire, thereby making it round. The wear on my tires is about 3/32s. Is it feasible to use the machine and shave off 3/32s from the new tire, making the diameter similar to the three worn tires, thus avoiding the expense of buying four new tires?
A: Making sure all four tires on a 4WD or AWD vehicle are the same diameter is critical. Any significant difference can put significant stress on driveline components. Your options are twofold: Have a new tire shaved to the same tread depth as the existing tires or mount four new tires.
I'm curious — how did just one tire end up worn to the point of needing replacement soon (4/32 to 5/32") while the other three are worn only 3/32" from their original approximately 11/32" (roughly half as much)? Remember this — your tires are absolutely the most important safety components on your vehicle. They are literally your only contact with the road surface. They are also relatively low-cost compared with other major components on the vehicle.
I don't see any long-term savings or advantage in shaving one new tire. Buy four of the best and highest-quality tires that are made for your vehicle. Trade in or sell the three lightly worn tires.
The bottom line is simple: Tires are the last part of an automobile to skimp or try to save a few bucks on. Your life is riding on this.
Q: My 2002 Honda CRV key fob does not open or lock the doors. Pressing the button only gets the lights to flash. I can open or lock the doors by using the key in the driver's side door lock. The dealer wants to trace the fault at $100 per hour. I have replaced the fob battery twice. The fuse is good. I suggested replacing the key fob, but they won't do it.
A: Since the lights flash when you push the keyless entry remote fob, I don't think the fob is at fault. I'd focus on one specific module — the Multiplex Control Unit which, among many functions, controls the electric door locks. Disconnect the battery, then unplug and check the under-dash fuse/relay box connectors for corrosion or poor-quality contacts. Since the door lock actuators appear to work when you use the physical key in the driver's outside door lock to unlock all the doors, the individual circuits from the module to the actuators would appear to be good. That makes the Multiplex Control Unit the prime suspect.
Q: My 2015 Volvo XC60 came with free regularly scheduled maintenance that calls for oil changes every 10,000 miles. The service manager said that with the synthetic oils and modern filters, more frequent changes are not necessary and that if it were his car he would not do it.
A: I found this in my ALLDATA automotive database. "Because this manufacturer [Volvo] does not specify a Severe Service Interval, the determination of the proper maintenance interval should be left to the good judgment of the vehicle owner and the advice of an authorized service center."
I would suggest that since you, rather than the dealership, own the vehicle, you make the call. I change oil and filter every 5,000 miles.