What you don't know about your car's oil is probably costing you time and money.
Too many dealer service lanes and quick lube places still make you feel like a bad parent if you don't change your car's oil every 3,000 miles, But the 1970s are over and so is that requirement.
Engines are built to more precise tolerances today, meaning there is less internal slop that leads to wear and less need for oil to operate as a cushion between warring parts. Oil is absolutely vital, but advanced machining and metallurgy ensure longevity more than ever.
Modern cars often have adaptive indicators on the dash that monitor your drive time and frequency, temperature cycles and engine RPM over time to deliver an adaptive oil change interval recommendation. If you use your car to make pizza deliveries in Manhattan during heat waves, it may suggest an earlier oil change. Most other driving behavior will fall under the standard recommendation.
The main way oil itself fails is viscosity loss, when it becomes thin and less cushioning due to its molecular chains breaking down under heat and pressure. Your oil effectively becomes a lower viscosity rating when that happens, offering less protection. But today's common synthetic oils simply resist that kind of breakdown far better than the old non-synthetics.
The modern car doesn't subject oil to high temperature swings the way cars did a few decades ago; You almost never see one boiling over on the side of the road today. These bulletproof cooling systems mean engine oil is seldom cooked the way it once was.
Aside from all this engineering, there are some interesting market factors to think about.
A few car buyers are intent on keeping a car until it has 300,000 miles or until they die, whichever comes first. Have at it. Most of us won't want a car that obsolete down the road; it would be missing too many safety and technology advances.
There's an old-school theory out there that carmakers want your car to wear out sooner than later so they can sell you a new one. I can't imagine many consumers buy the same kind of car after a systemic engine failure. Quite the contrary.
The growth of leasing is also a huge factor. 3.9 million cars will come off lease and often be returned to carmakers in 2018, needing to sold or leased again with an extended factory warranty. Carmakers don't want a bunch of time-bomb engines on the lot that they'll be on the hook to fix down the road. We all think engineers and designers run car companies, but CFO's really do and these kinds of costs are very much on their minds.
There was a time when changing your oil much more frequently bought you meaningful insurance. That was also when seat belts were optional.