Q: Whenever I have wheel or tire work done, the shop always makes a note on the repair order to return after 50 to 100 miles to have the lug nuts retightened. Is this necessary, or are the tire dealers just covering their butts in case of a screwup? It is hard to believe that lug nuts properly tightened with a torque wrench would work loose. If they did, why wouldn't they work loose again in the next 50 to 100 miles? Wouldn't continually checking them be ludicrous?
S.P., McGraw, N.Y.
A: Only new wheels (or wheel studs) need to be re-torqued once more after 50 to 100 miles. Compression of the wheel's metal or elongation of the new studs could occur. This would only happen once. By the way, when the nuts are re-torqued, the wheels should be cool and the nuts loosened and then torqued to the manufacturer's specification. As to whether your tire dealer is covering his butt is a question we are not prepared to answer.
Q: I drive a 2013 Mercedes GL350. The SUV requires diesel fuel. You recently referred a reader to pure-gas.org to find ethanol-free gasoline. I am looking for pure diesel fuel for my vehicle and cannot find any in my area. I am concerned that the biodiesel available at my local gas stations is damaging my vehicle. Do you know of any stations in my area that provide pure diesel fuel?
M.M., Glen Ellyn, Ill.
A: Mercedes-Benz's published statements say "Diesel fuel with up to B5 biodiesel content according to ULSD (ultra low sulfur diesel) specification ASTM D975 meets Mercedes-Benz approved fuel standards and will not void coverage under the Mercedes-Benz New Vehicle Limited Warranty. Diesel fuels between B6 and B20 or higher pose risks of engine and fuel system damage, and are not approved by Mercedes-Benz. Please refer to the following recommendations to help avoid engine and fuel system damage if you do not have the chance to refuel your vehicle continuously with ULSD, maximum B5: Fuel with biodiesel content greater than 20 percent, including B100, is not approved by Mercedes-Benz due to the risk of severe engine damage. Any damage caused by the use of such non-approved fuels will not be covered by the Mercedes-Benz New Vehicle Limited Warranty." The TDI Club (tdiclub.com maintains a forum where you will find a link to locations selling non-biodiesel fuel . Truck stops are often a good bet. Always check the pump for accurate fuel labeling prior to refueling.
Q: I own a 2001 Dodge Ram Van. I have had to change the resistor block that controls the heater and air conditioning blower five times. In all my years of driving, I only had to replace this resistor once, and that was on a 1973 Dodge Dart. The three resistor coils look fine. However, there is another component that is not a resistor and I am wondering if that is what fails. Although it is the same size as a resistor, it does not look like a resistor because there are no colored bands on it. Is this some kind of fuse?
J. W., Chicago
A: Bingo! It is a fuse — a thermal fuse that pops when things get too hot. But the fuse does not blow randomly. The blower motor is probably drawing too much current. Replace the motor the next time you have to replace the blower resistor.
Bob Weber is a writer and mechanic who became an ASE-certified Master Automobile Technician in 1976. He maintains this status by seeking certification every five years. Weber's work appears in professional trade magazines and other consumer publications. His writing also appears in automotive trade publications, Consumer Guide and Consumers Digest. Send automotive questions along with name and town to motormouth.tribverizon.net.