Q: I own a 2005 Chevy Malibu with 75,000 miles on it. I have kept up with oil changes religiously since buying the car new. I am considering buying a new car. However, the Malibu is in great shape for 10 years old and runs like a top. The body and interior rate eight on a scale of 10. Should I buy a new car simply because of the age of the Malibu, or keep the Malibu and give it a major tuneup — change the antifreeze, brake fluid, transmission fluid, serpentine belt and the plugs, wires, and air filter. What would you do?

Q: I have a 2003 Toyota 4Runner with 150,000 miles on it that I have owned since new. It has been a great, trouble-free vehicle with the original starter and alternator. Even though these two components are working fine, how much life do you think they have left? Should I replace them or wait and get as much mileage out of them as I can at the risk of leaving me stranded?

A: Today's motor vehicles and their components are so well engineered and built that 75,000 miles is no more than half the vehicle's service life — often less! So the answer to these types of automotive questions is related more to economics then mechanics.

Compare the costs of dealing with starter or alternator failure vs. pre-emptively replacing them. According to the repair cost estimate in my ALLDATA automotive database, installing a factory-new alternator and starter on the 4Runner would cost nearly $1,000. Installing remanufactured parts would save several hundred dollars.

I pay $40 per year for roadside assistance on my older vehicles. This would cover the tow to a repair shop for a failed starter or alternator — not both at the same time unless you have truly angered the automotive gods. Since a failed alternator is more likely to strand you than a no-start failed starter, a brand new alternator installed would run roughly $600, less for a "reman." Add to this the fact that there's no expectation of an alternator or starter failure — "stuff" just happens. It is just as likely the A/C system could fail before the starter or alternator. Would you replace the compressor on a pre-emtive basis? I wouldn't. Nor would I replace a starter or alternator until a problem developed.

Should the Malibu be replaced just because it's 10 years old with 75K miles? Heck, I typically buy precisely this age/mileage vehicle. Why? It's already hugely depreciated. The MSRP on an '05 Malibu was $20K-$25K. Today, that car with those miles is worth about $3,300 in trade, $5,800 retail. Drive it five more years with the same annual mileage and it might be worth $1,400 in trade, $2,200 retail. Depreciation of $1,900 to $3,600 is a mere fraction of the depreciation on a new $20K-$30K vehicle over the next five years. Not to mention lower annual license and insurance costs for the older vehicle.

Even if you budget several thousands of dollars for maintenance and repairs over the next five years, keeping your '05 Malibu makes economic sense.

Absolutely, without question, the best way to minimize your cost-per-mile of ownership, operation, licensing and insuring a motor vehicle is to drive it as long as possible. With the quality of today's motor vehicles, that means keeping a new car at least 15 years and 150,000 miles.

In simple terms, buy the right vehicle, drive it right, take care of it right and keep it for its full service life — that's the way to get the most out of your automotive dollars in today's world.

Motoring note: As several readers so kindly pointed out, the smaller-diameter tire will roll more times per mile, not fewer as I stated in last week's column. I'm claiming dyslexia, distraction, faulty calculator and senility! That's my story and I'm sticking to it.