Q: I was told, and I just verified, that my new car does not have a spare tire! This really concerns me. Why in the world would they build a car like this? What can I do to be sure I don’t have a problem with this in the future?

A: You’re not alone. Approximately one-third of new cars are no longer equipped with a spare tire. This is an unpopular compromise to save weight for improved fuel economy and to free up trunk space. Spare-less cars may be equipped with either run-flat tires or a cheesy inflation kit consisting of a container of sealer and a small compressor. The stiff sidewalls of run-flat tires allow one to continue to drive at reduced speed until service can be performed.

Given this situation, and if a compact spare isn’t available as an option or recycling yard score, I’d consider carrying a few additional items to level the playing field. Should a nail or screw become imbedded in the tire, don’t remove it! If a bare puncture is discovered, I’ve had good luck threading a 1-inch sheetrock screw into it (a Phillips-head screwdriver is needed) to temporarily seal the leak. An inexpensive tire plugging kit can also help with larger holes.

Q: I have a 2004 Mercedes E500 with 91,000 miles. It has been maintained very well and seems to run perfectly. Recently, after about a 35-mile highway drive, I got what seemed to be a little transmission slippage when I accelerated from two or three traffic lights. After the first upshift, it was fine. The next day, and for several days since, I have noticed no problem at all, although I have not done any highway driving. I would like to take this vehicle to Florida at the end of January. Can you think of anything that would cause this problem and how extensive and costly would it be to repair?

A: Your Mercedes has a mechanically robust transmission but is known for some fairly easy-to-fix electrical bugs. There’s a good chance your intermittent fault may be caused by problems with the transmission’s conductor plate or pilot bushing. The conductor plate is a large plastic gadget that electrically connects the solenoids and sensors within the transmission to the wiring connector that exits the transmission case. A variety of electrical faults causing odd shift functions are common as this part ages. The pilot bushing is a plastic sleeve that helps seal transmission fluid from leaking into the wiring harness and outside, to the ground. Fluid wicking into the vehicle wiring harness can cause performance oddities and possibly make its way to the control computer, damaging it. Start with a fluid level check, a scan check for diagnostic trouble codes and inspection of the transmission electrical connector for fluid seepage. The parts should total around $150 to $250, depending on the source. Renewing the pilot bushing is easy. The conductor plate requires valve body removal and reinstallation, which is about three hours of work plus filter and fluid. These parts are also used on quite a few other Mercedes models and some Jeep Cherokee SUVs and Dodge Sprinter Vans.