Can Classic Cars Use Synthetic Motor Oil?

Technically, the first synthetic oils were produced in 1877, which was about a decade before the first patented motor car arrived in 1885. Despite this, the former didn't find its way into the latter until the 1920s. Even then, it didn't get popular until the '70s, when the OPEC oil crisis caused shortages of the real stuff. Anyway, the point is that vintage cars weren't originally engineered for synthetic oil. A car like the Model T used so-called light oil at a time when your only choices were light, medium, or heavy.

The good news for vintage-car enthusiasts is that those old engines aren't nearly as finicky as today's. Putting the wrong oil in a modern motor can be a recipe for disaster, but you can even put diesel motor oil in your gas-powered classic. So, it should come as no surprise to learn you can use synthetic oil, too. In fact, some automakers come right out and recommend it for their older engines. 

Not all that much, from a chemical point of view. Both ultimately contain the same kind of hydrocarbon molecules, but in real oil, the overall molecule structure can be more random because that's just the way nature is. With typical synthetic oil, the molecular structure is built up piece by tiny piece. This lets scientists create an oil with a standard, uniform molecular structure for highly consistent performance. 

In most cases, synthetic oil starts with a base material that comes from good old crude oil. A newer method of producing synthetic oil, however, relies on natural gas that's chemically transformed into hydrocarbon oil. The GTL (gas-to-liquid) oil is purer than regular synthetic oil, which is, in turn, purer than crude oil. Of course, the purer the oil, the more it will cost you, but you're likely to see better results as well.

For one thing, proper lubrication helps ensure your engine runs more efficiently, and that can translate into improved fuel-economy when you're out and about. Synthetic oils will also help you go longer between oil changes, and included detergents can make a further big difference by cleaning out waste deposits that may be left behind by regular oil. There are even synthetic oils with extra zinc for older engines, where a zinc additive is needed to protect against wear and tear.

When synthetic oils began appearing on the market in the latter part of the 20th century, the companies that produced crude had the expected response: resistance. This included the typical kind of misinformation program now seen with big oil's use of TikTok to influence young people today.

The lingering effects of the push against synthetic oil is a list of commonly cited disadvantages that are distinctly wrong. For instance, folks may say that synthetic oil is more expensive compared to oil sourced from the ground. However, this does not take into account the fact that synthetic oil lasts longer, so you don't have to change it as often, which means you don't have to buy it as often.

Another misleading claim is that synthetic oil can damage seals in your car's fuel system, which isn't true either. Sometimes you'll have a cracked seal somewhere along the line and not notice it, because dirt and grime in the system are essentially filling in the crack. Synthetic oil can help you discover that kind of leak since its added detergents may be enough to clean that gunk out.

There are also people who will tell you to only use synthetic oil in high-priced or high-performance vehicles, or who claim if you switch from regular oil to synthetic you can't switch back. Don't listen to them — the benefits of synthetic oil are definitely real.