Motormouth: New bulb didn't fix minivan's rear lights

I have a 2009 Dodge Caravan. The right rear brake light is not working. Turn signal light is not working. Flasher light is not working. The taillight is the only thing working. The right blinker arrow in the dash blinks fast. I changed the bulb, but that did not fix it. What is the next step before seeking professional help?

D.C., Chesterton, Ind.

A: Your vehicle uses a dual filament bulb. One filament glows for taillights, the other, brighter one is activated for the brake and turn signal lights. The rapidly blinking turn signal arrow is the way of letting you know that there is a bulb out. But since you replaced the bulb, chances are there is a problem with the socket, the connection or the wiring. You may have to turn to a pro.

Q: Why do higher-end manufacturers provide drilled brake rotors (particularly on performance cars)? I've asked dealership personnel, and typically I get a non-answer. I'm of the opinion that slotted rotors do a better job of relieving any built-up gas pressure. Certainly there is a cost involved over nondrilled rotors. Your thoughts?

R.R., Lisle, Ill.

A: Most people think that the drilled holes or slots in brake rotors are there to cool them under heavy braking. While this is not wrong, there is a better reason. Under heavy braking, the friction material on the brake pads may become hot enough to smoke, so you are right about relieving gas pressure. The holes and slots carry the smoke from between the pads and rotors for improved braking performance.

Q: I recently purchased a Cadillac XT4 with a 2.0-liter turbo four-cylinder engine. The owner's manual states to use premium fuel. I spoke with the dealership about using regular grade gas and was told that by not using premium, the mileage per gallon could be reduced and might also cause engine ping. I don't want to use high-grade gas if it's not necessary. What is your advice?

A: Your Caddy will get better mileage with the higher-octane fuel than a lower-octane fuel. That is because, should ping be detected by the knock sensor in its engine, the engine control module will back off the ignition timing until the knock stops. Since your engine is getting de-tuned, your mileage will suffer.

Q: Following up on your column about highway signs, here's another catchy warning phrase that the Minnesota Department of Transportation has posted on signs over our freeways: "Not wearing a seat belt? What's holding you back?"

R.C., Minneapolis

A: Love it. I invite my readers to submit clever signs they have seen, and we will run some from time to time. We could all use a few more smiles to go with the miles.