Today’s cars don’t need highway miles to survive

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 t hecarengine in good shape? If so, how frequent and how far as a minimum? – Jim

RAY: 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 clea nlynowthatifyou 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 .Sod oing 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 premature ly. 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 wo rryab ou tit,J im. Got a question about cars? Write to Car Ta lkinc ar eofKing Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.