Motormouth: Have turn-signal light bulbs become obsolete?

Q: Regarding the need for routine light bulb checks, you can eliminate turn signal indicator lights. Nobody uses them anymore.

L.K., Chicago

A: We still see a few old-timers using turn signals, but have you ever stopped to consider that some motorists may have simply forgotten to refill their blinker fluid?

(Editor's note: Blinker fluid is not a thing. It's a joke.)

Q: I read your article Sunday, as always, and I had to write. M.T. writes about technicians checking lights as a part of regular service. The next time you are on the road and get sick of playing I Spy or the License Plate Game, start playing GM SUVs and Pickups With Only One Working Daytime Running Light Game. My buddy pointed it out to me. It has gotten comical. We wonder if the guy who designed the running lights for GM/GMC still has a job.

G.W. Lemont, Ill.

A: Frankly, we have never paid close attention, but we will now. GM seems to have put the issue, which pertained mostly to 1999 through 2003 vehicles, behind it. According to a technical service bulletin: "A new 14-volt DRL bulb, P/N 15199562 (trade bulb 4114K), is now available for use whenever a DRL lamp bulb requires replacement. This more robust, higher-voltage DRL bulb replaces P/N 1999482 (trade bulb 4157K). These bulbs should be replaced in pairs for customer satisfaction."

F.T., Skokie, Ill.

A: Since we have not seen the condition of the calipers, pads and rotors, we cannot make a judgment. But the work does seem premature, especially for rear brakes. Virtually nobody rebuilds calipers anymore. It is quicker to install new ones or remanufactured calipers. Throughput is the name of the game. In an effort to reduce weight and increase fuel economy, today's rotors are very thin and cannot be machined in most cases.

Q: My previous 2000 Chevy Malibu took 5W-30 oil. My current 2013 Malibu calls for 5W-20 oil. I have leftover quarts of 5W-30 oil. Is it OK to use the 5W-30 oil in the 2013 Malibu or even equal parts of 5W-30 and 5W-20?

J.A., Cetronia, Pa.

A: More important than the Society of Automotive Engineers viscosity grade (e.g. 5W-30) is the American Petroleum Institute classification of the oil. Your old Malibu required oil meeting the API SM classification. Your new car requires oil meeting the SJ classification. If the oil on your shelf has the SJ rating, you may use it with no adverse consequences.