Synthetic Oil Lifespan: How Long Does It Really Last?

Synthetic motor oils have been around for a while now, longer than most gearheads realize. The first synthetic hydrocarbon oils were created by French chemist Charles Friedel and his American associate James Mason Crafts in 1877. Thirty-six years later, in 1913, a German scientist named Friedrich Bergius figured out a process for creating synthetic oil from coal dust. A few years later, a pair of his countrymen named Franz Fisher and Hans Tropsch figured out how to make synthetics out of a combination of hydrogen and carbon monoxide.

Standard Oil tried to commercialize synthetic oil in 1929, but it didn't stick due to lack of demand and, well, we had that Depression going on at the time. Scientists from all over the world kept working on it, though, and synthetic oil technology kept inching forward. Synthetics got a huge boost during WWII as the Nazi war machine started using it due to sanctions and dwindling domestic oil supplies. Not the best pedigree, you'll agree, but the Wehrmacht trying to figure out how to keep tanks and trucks running without oil gave synthetic technology a huge boost.

After the war, research continued but it wasn't until the 1970s American fuel crisis that synthetics really took off. Today, many cars are shipped from the factory with synthetic oil, and thousands of gallons of digital ink has been spilled on blogs and forums outlining the pros and cons of using it. One of the most contentious arguments about synthetic motor oil — aside from whether or not a true blue gearhead should use it at all — is how long it lasts and how often you should change it.

Modern synthetic oils last an incredibly long time. Thanks to all the detergents, additives, and other concoctions in them, these oils might be good for anywhere from 7,500 miles to 15,000 miles. Extremely high-grade synthetics like Mobil 1 can last as long as 15,000 miles. That's under perfect laboratory conditions, however. Brands put those numbers on the bottle assuming that you'll be driving sedately in light traffic or on the highway. 

Actual, real world driving in adverse conditions — heavy traffic, extreme high or low temperatures, dusty, dirty conditions, etc. — can reduce those numbers pretty easily. Driving your car without getting it all the way up to operating temperature also usually counts as adverse conditions, and a lot of short hops with long stretches of inactivity between them can break even the best oil down pretty quickly.

Your best bet, honestly, is to change your oil per your vehicle manufacturer's recommendations as laid out in the owner's manual. These days those reccos can run anywhere from 5,000 to 7,500 miles between oil changes, which seems like madness to those of use raised with the old "every 3,000 miles" rule. The fact is that modern motor oil, whether it's synthetic or good old fashioned dinosaur squeezins, is leaps and bounds better than it was in the '80s or '90s. Obviously, it's your vehicle and you should care for it as you see fit, but you can generally trust those manufacturer reccos and long-lived oils.