Q: In regard to your statement that it is safe to use regular gas in a car for which the manufacturer recommends premium, how new is the knock sensor technology? Would it be present in my 2012 Infiniti M37x? What about my 1989 Mercedes Benz 560SL?

J.O., La Grange Highlands, Illinois

A: According to an SAE (Society of Automotive Engineers), the first use of a knock control system was on the Toyota Crown in 1980. Yes, your Benz has a knock sensor.

Q: I have a 2016 Toyota RAV4 XLE with AWD. We do a combination of highway and city driving with normal trips being 20 and 60 minutes (no short trips so the engine is always fully warmed up). However, we only put around 6,000 miles on it in a year lately.

I also use only Top Tier fuel (usually Shell or Costco) and regularly dump fuel system cleaner in the gas tank at least once or twice a year. The car has 81,000 miles on it. The engine runs fine, and my gas mileage/performance seems normal. Recently my service center mentioned doing a fuel induction cleaning service on the vehicle.

What are your thoughts?

B.S., North Aurora, Illinois

A: Based on age and mileage, I would go for it. The fuel induction system includes the air filter, the mass airflow sensor and the throttle body. The cleaning focuses on the MAF and throttle body. After the service, you might find improved fuel economy.

Q: I have a 2009 Buick Lucerne, 6-cylinder, 3-liter and 69,900 miles on the car. My engine has been leaking little bits of oil steadily for the past 6 years. I was told that the whole engine needs to be taken out in order to be fixed, but it is a small leak and the car can be driven. But now I think it is leaking more oil. Should I go ahead and fix it or buy a new car? Which is a better option and cost effective? Although the car is long and big, I like it. New cars cost so much. I would appreciate your input.

A.G., Chicago

A: As usual, it boils down to money. Your car needs a rear main seal. The seal is under $100, but the labor can be $700-1,100. But where are you going to find a reliable replacement car for around $2,000? Before I’d lay out that kind of money, I would pour some rear main seal stop-leak in the oil. Popular brands are Bar’s, Lucas and Blue Devil. Although they probably won’t stop the leak, they might slow it down.

Q: The Lexus dealer serviced my brakes this year, and now my brake pedal makes a clicking noise when I apply it. It makes the noise when the car warms up or when I am driving in traffic.I complained about the clicking noise to the dealer. They inspected the brakes and said the brakes were fine and the clicking noise is normal. Do you have any comments?

B.T., Chicago

A: Let’s hope the sound is not coming from the ABS control module. It could be an expensive fix. But it is probably something mechanical in the brake assembly under the dashboard.

Q: Since some cars are misreading highway route numbers as speed limit signs, maybe it would be easier to change the law so you can drive the speed limit based on the route number. If you're on I-55, you can drive 55 miles per hour. If you're on I-80, you can drive 80 miles per hour. What do you think?

J.C., Naperville, Illinois

A: I think you’re nuts!

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