Q: We own a 2014 Mercedes E350. The owner's manual states that spark plugs should be replaced at 60,000 miles or six years. At the six-year service, the car had only 44,600 miles. The service writer tried to convince me to include the replacement of the spark plugs because of the age. I am leaning more to doing the change at 60,000 miles. My thought is that the primary impact of not replacing the spark plugs now would be decreasing the gas mileage. Is that correct?

A: Your engine is equipped with platinum tip spark plugs. They age very slowly, meaning that the gap between the electrodes does not widen. It is a widening gap that decreases fuel economy. Many carmakers require replacement of them at 100,000 miles, so you will be safe at 60,000.

Hot stuff

Q: I own a 2005 Corvette in southern Nevada and never drive the car when it's above 110 F. I am afraid I could damage the car because the coolant temperature can reach 218 to 220 degrees in stop-and-go traffic. I think that is too high, but I'm not an expert. At outside temperatures below 100, the coolant temperature will hold at 190-195 most of the time. Above 105 degrees, the coolant temperature is at 194-198 on level stretches of the highway and up to 200 climbing hills. Does that sound like a problem to you?

A: Coolant, the 50-50 mixture of antifreeze and water, boils at 226 degrees. Manufacturers test their vehicles in hot as well as cold climates. GM used to test theirs at their proving grounds in Mesa, Ariz., but recently moved it to Yuma, Ariz. Yeah, it gets hot in Nevada, too, but the cars are designed to handle it.

Outgassing info

Q: In your column three weeks ago, one of the items mentioned outgassing, but there is no description of that phenomenon. What is it, exactly?

A: It refers to a trapped gas being released from something, such as the vinyl of your dashboard.

Finicky filter

Q: I had my 2013 Nissan Altima 2.5 in for a routine oil change. Within 10 days, drips of oil were noticed on the driveway. We checked the oil plug and filter. The plug was fine, but the oil filter was loose. We tightened the filter and called the mechanic where the oil was changed.

We were told they were having problems with a specific oil filter loosening up; I was the fourth customer who had called to report it. They gave me another oil change at no charge.

We have been changing oil in our cars for about 40 years and have never heard or seen an oil filter loosen on its own. Does this make sense?

A: This sounds like a manufacturing defect. The shop might have changed brands or suppliers. With so many complaints, they should drop that brand. It is good to hear that they gave you a free oil change.

Bob Weber is a writer, mechanic and ASE-certified Master Automobile Technician. His writing has appeared in automotive trade publications, Consumer Guide and Consumers Digest. Send automotive questions along with name and town to motormouth.tribune@gmail.com.