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Yes, You Can Put Synthetic Oil in a Classic or Just Plain Old Car

Car and Driver logo Car and Driver 12/3/2020 Annie White
  • Modern synthetic oil is safe to use in all types of vehicles, ranging from new purchases to classics to aging not-so-classics.
  • The idea that synthetic oil could harm old engines probably comes from a time before synthetic oils had been extensively tested.
  • Whether you use synthetic or conventional lubricant, be sure to follow the manufacturer's guidelines for oil viscosity.

So, you have a classic car and you want to put synthetic oil in it, but something you read on the internet or something your dad told you 20 years ago or just plain old anxiety is staying your hand. Never fear. We're here to clear up any confusion you have related to your car's vital fluids. We'll start off slow. Yes, you can use synthetic oil in your classic car. Or your 20-year-old Taurus. Or really anything you've got on hand. Feel better?

If you're still skeptical, allow us to break it down. Synthetic oils are composed of chemically engineered molecules designed to provide higher performance and better protection for your engine than conventional oils, which are derived from crude oil without significant intervention from chemical engineers. Synthetic oils tend to offer better performance at extremely high or extremely low temperatures and retain their lubricating properties longer than conventional oils do.

a store inside of a car: gettyimages-1279072796 © Bob Riha Jr - Getty Images gettyimages-1279072796

The idea that synthetic oils are bad for older cars probably comes from the fact that early synthetic oils (we're talking 1970s) contained a chemical compound that could damage engine seals and, in some cases, cause leaks. These days, all types of motor oils are tested to make sure they won't damage your car's engine, and synthetics no longer use the chemical compound (ester) that caused these problems. If you won't take our word for it, look to the manufacturer. You should be able to find recommendations for oil in classic cars, and it's not uncommon for full synthetic to be the oil of choice. You can even look for a stamp of approval from your car's manufacturer on the back of the jug of oil, which will tell you that the company has tested that oil for compatibility with its engines.

a store shelf filled with books: gettyimages-1189380042 © Jeff Greenberg - Getty Images gettyimages-1189380042

If you're dealing with an owner's manual and recommended service intervals that were written before synthetic oil came onto the scene, you may find that you can go longer between changes after you make the switch. These oils are engineered to last longer before breaking down, so they won't start leaving sludge in your engine as soon as conventional oils would. Some synthetics have additives that are designed to help slough off sludge. If you're switching to synthetic oil for the first time, consider easing into the longer change intervals in case there are significant deposits left from bygone lubricants.

There is, of course, one downside to using synthetic oil: it's significantly more expensive than the conventional stuff. It's up to you to decide whether the performance benefits and the longer intervals between changes outweigh the cost. No matter what type of oil you decide to put in your car, make sure to follow the manufacturer's recommendation for viscosity.

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