Hartford Courant (Sunday)

Today’s Cars Don’t Need Highway Miles To Survive

- By RAY MAGLIOZZI King Features Syndicate Got a question about cars? Write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.

DEAR CAR TALK: I’m retired, and at age 70, I hit my midlife crisis and bought my first Mercedes (new). But being retired and living downtown in the city where I can walk to most things, I find myself doing city driving almost all the time. So is it necessary to get on the freeway once in a while to keep the car engine in good shape? If so, how frequent and how far as a minimum? I enjoy your column!

— Jim

No, there’s no need to drive your car on the highway, Jim.

People used to tell you to take your car out on the highway and “blow out the carbon.” But there is no more carbon. Modern engines with fuel injection, computeriz­ed engine controls and improved gasolines run so cleanly now that if you take your engine apart after 50,000 miles, the tops of your pistons will be as clean as they were when you drove off the lot.

So doing only “in town” driving is no problem. And if you’re driving for at least 15 or 20 minutes on a semi-regular basis, you’re probably getting the exhaust system hot enough to evaporate most of water vapor that condenses in there when the exhaust system is cold.

If you take all five-minute trips, you could cause your exhaust system to corrode prematurel­y. An exhaust system on this car could run you a few mortgage payments. On the other hand, the exhaust system on a Mercedes is pretty robust. So even with all those short trips, corroding the exhaust might take 10 years.

And by then, your ne’er-do-well son probably will have talked you out of this car, and you’ll be driving a 2028 S-Class. And we can let him replace the exhaust.

Enjoy your car, and don’t worry about it, Jim.

DEAR CAR TALK: “Dad, my car won’t start” were the first words of a phone call from my daughter who is 1,500 miles away. Her typically reliable 2015 Madza 3 with less than 25,000 miles had stopped working. Specifical­ly, the push-button start didn’t start the engine. Pushing the button repeatedly brought no response at all.

I first suspected the key fob (weak or dead battery). That was ruled out when the key fob was able to lock and unlock the doors from 50 feet away. After attempting the starting process several times and asking the typical “dad” questions (“Is the car in park?” “Is your foot on the brake?”), she exclaimed: “It started!” I had her drive immediatel­y to the dealer since it was still under warranty. Of course, the car started perfectly then.

A subsequent examinatio­n revealed a defective brake light switch. In today’s cars, this switch doesn’t only activate the brake lights when the pedal is depressed; it also sends a signal to the computer that the brake has been engaged and it’s OK to start the car. The faulty switch resulted in an intermitte­nt signal.

My question is, given the critical role that this once-simple part now plays in modern cars, why hasn’t it been re-engineered to be much more robust and reliable?

— Pete

It probably hasn’t been re-engineered because not enough of them fail, Pete. As you say, the brake must be depressed in order to start the car. That’s a carryover from the 1980s, when Audis were thought to be possessed with “unintended accelerati­on” demons.

Upon investigat­ion, they found that at least some of the cases of cars accelerati­ng through the back walls of garages were caused by people stepping on the gas when they thought they were stepping on the brake.

So carmakers started engineerin­g “interlocks.” They made it so you couldn’t shift out of park unless your foot was on the brake. And then, when keyless ignition came into use, they required your foot to be on the brake before the car would start.

And the simplest way to engineer that stuff was to use the existing brake light switch — which was already signaling when the driver’s foot was on the brake. While we know that most carmakers won’t use a 5-cent part when a 4-cent part will do, to be fair to them, I can’t remember the last time I replaced a brake light switch.

So in general, they seem to be pretty darned reliable.

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