Chemistry, maintenance are keys to longevity

Today's cars with six figures on their odometers look and drive better than ever thanks in large part to chemistry.

Changes made at the molecular level in rustproofing; steel body panels; engine and transmission parts; paints; rubber components such as seals in the drivetrain; and suspension bushings have ensured that many older cars have plenty of life — and value — in them after they pass 100,000 miles.

That's being recognized by a growing number of franchised dealers who are selectively adding well-maintained high-mileage used vehicles to their inventories and selling them profitably, a scenario that is expected to continue even after the new- and used-car markets return to normal.

These higher-mileage used vehicles, which are often sold at attractive prices, are opening a new segment for dealerships: cash buyers.

Alex Rose, a veteran salesman at Village Jeep in Royal Oak, Mich., a suburb north of Detroit, recently sold for cash a 2008 Jeep Grand Cherokee with 240,000 miles. The store was also offering a V-6 2011 Jeep Wrangler with 174,000 miles. The black off-road vehicle featured glossy unblemished paint, a clean interior, no rust or major cosmetic defects and an engine that runs smooth and quiet.

Peter Votruba-Drzal, global technical director, automotive, industrial and mobility at PPG Industries, one of the largest suppliers of automotive paints and rust preventative undercoatings, credits rust reduction by automakers as one of the reasons vehicles are living longer.

Nearly 50 years ago, PPG pioneered electrocoating technology that uses electricity to bond liquid rust preventative to raw steel. It's also a foundation for paint.

"Electrocoat was a new-to-the-world technology that allowed car bodies to be completely submerged into a bath of charged paint. When you apply voltage, you can apply on any conductive surface a continuous layer of barrier coating. That was critical to improving the overall corrosion performance of the vehicle." The coating, he adds, gets into rocker panels and other areas that are not accessible to paint guns.

PPG and other companies have also developed paints that are more resistant to chipping and fading. Votruba-Drzal says advances in artificial weathering have been used to improve paint durability. Clear coat also has been a major factor in protecting painted surfaces by helping to prevent scratches and fading. To further keep rust from starting, automakers, he added, have learned how to design bodies that don't trap moisture, and they have increased the use of rust-preventative zinc-coated metals.

Automakers won't publicly talk about how long their vehicles should last. There are too many factors that affect longevity for them to give a precise answer — maintenance, where and how the vehicle is used and how it is stored all affect its longevity. Stellantis and Honda, for example, declined to comment for this report. But major industry suppliers know the parts they are making will not wear as quickly these days.

The automatic transmissions made by German supplier ZF, for instance, should not have to be replaced.

"Under normal treatment, our ZF automatic transmissions will survive the service life of the vehicle in which they are installed. For light vehicles, this regularly means more than 200,000 miles. In fact, even within light commercial vehicles, ZF has inspected transmissions (for study purposes) at nearly 525,000 miles without failure," John Hawkins, ZF Group's vice president, electrified powertrain technology, said in an email.

Federal Mogul, recipient of several Automotive News PACE Awards for such innovations as diamond-coated piston rings; advanced pistons; and long-life, high-heat gaskets, spends millions on R&D yearly on products that have extended the life of engine components.

FEV North America, a product development and testing company just north of Detroit, works with virtually all automakers to ensure powertrains last far past warranty periods without major failures. Michael Franke, senior vice president, engine and hybrid powertrain systems, says a well-maintained modern engine used in moderate conditions — that is, not exposed to excessive heat or cold or extreme use — is nowhere near worn out at 100,000 miles.

"You cannot treat every engine the same because of different displacement, power densities and vehicle weight. But a moderately operated and loaded engine should go significantly above 200,000 miles," he said.

Franke credits chemistry, precise controls of the engine's fuel, ignition and temperature, as well as improved transmissions with a greater number of gears for the durability of today's engines. More precise manufacturing is also a factor.

"Certainly, technical changes have led to increased durability and robustness. Two to mention are improved materials and production processes. Coated [rod and crankshaft bearings] improve wear protection; other wear surfaces are prepared with diamondlike coating that improves the wear resistance," Franke said. "The typical weakness of past engines was obviously oil leakages. That has been improved with sealing functions and techniques and better-prepared surfaces. Those have led to more engine and powertrain durability over the years," he said.