What oil should you use in your older or classic car?

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If you have an older vehicle, you likely change its oil on a regular basis. But are you using the right oil for it?

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Older vehicles – generally 1990s and earlier – can have special needs. They were designed to run the lubricants available at the time, and just as engines and driveline components have evolved, so have the fluids that go into them. The right ones can be a factor in component performance and longevity.

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What oil should you use in your older or classic car? Back to video

“It’s about all the normal things one could expect from lubrication, such as engine cleanliness, wear protection, helping the cooling system dissipate heat, and efficiency, such as how the engine uses the fuel you’re putting in,” said Nicolas Demaria, technical support manager for Motul, which recently launched a line of era-specific motor oils. “With the right additives, you can increase this efficiency. You can have engine performance with less pumping loss.”

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Auto enthusiasts have long been on both sides of the synthetic-oil issue — some say it can go into anything, while others believe it can cause leaks and other problems. Demaria warns that in very old cars, synthetic oil can affect organic engine gaskets, such as those made from cork, if they haven’t been retrofitted with modern materials. The Motul oils increase their levels of synthetic and detergent for different decades of vehicles, mimicking the gradual improvements made by petroleum companies over the years.

What’s synthetic all about?

Among all oil brands, exactly what synthetic oil is can be confusing. It sounds like it’s made entirely in a lab, but much of it – if not most – contains some dinosaur juice, whether as its base, or extracted from natural gas. It can be difficult to know for sure, since the label doesn’t have to specify exactly how synthetic an oil is, and most oil manufacturers don’t divulge exactly how they create their products, since they use proprietary processes.

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Generally, synthetic oil starts with petroleum, which is then distilled and refined to extract the highest possible amount of impurities. It’s then engineered into small, uniform molecules to create a synthetic oil base. Those uniform molecules improve flow, reduce friction and wear, and slow the oil’s breakdown and oxidation rate. From there, the manufacturer incorporates a proprietary blend of additives and detergents. You’ll see some oil labelled “synthetic blend” or “semi-synthetic.” This is synthetic oil blended with conventional oil. It’s cheaper than full synthetic, but here’s the thing: companies aren’t required to label how much of each type is in that bottle.

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Viscous about viscosity

Viscosity refers to how thick or thin the oil is at specific temperatures, which in turn indicates how well it flows under these conditions. Older cars ran on monograde or “straight-weight” oil, because that’s all there was. Multi-grade or multi-viscosity oils – such as 10W30, where the “W” stands for “winter, ” not “weight ,” as some think – arrived in the 1950s. As you know, the first number is viscosity in cold temperature, where you want the oil to stay fluid and not thicken in the cold; and the second is hot, where you don’t want it to become too thin.

Monograde oils are still widely available, primarily because they’re used in very hot climates, or in heavy-duty applications such as mining or construction equipment. These single-grade oils can be used in 1950s and older cars – generally SAE 30 to SAE 50 – but most owners use multi-grade. For subsequent decades, you’re best to follow the manufacturer’s oil-weight recommendations, especially with forced-induction or high-revving engines.

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According to Demaria, oils with a wider temperature range began appearing after gasoline prices started to soar in the 1970s and 1980s. “People thought about fuel efficiency and emissions, and tried lower viscosity, working with 10W30 and then 5W30 oil. In the late 1980s and the 1990s, a lot of (auto manufacturers) also started approving synthetics, especially Japanese and Europeans,” he said.

Zinc about it—

If you have an older engine with flat tappets (generally pre-1980s), or certain performance modifications, you’ll need to treat them to oil with zinc dialkyldithiophosphate (ZDDP), which lubricates them and prevents premature wear to the camshaft. Zinc got phased out when cars didn’t need it anymore, since it can harm catalytic converters.

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You can buy ZDDP additives, but it’s easiest to use oil that’s formulated for older or race-modified cars. This will have the appropriate level of zinc, or a zinc replacement, already in it. Don’t then fortify that oil with additives, thinking more zinc equals more protection, since too much zinc can also cause wear and corrosion.

Some oily tips

If a car isn’t driven much, or it’s stored during the winter, some owners only change the oil once a year. If you do, change it before it goes into storage, so it isn’t sitting with used oil in it. We prefer then changing it again when it comes back out.

Some people start their cars during the storage period, especially if they have to move them out of the way in the garage. If you do, let the engine thoroughly warm up before you button it back up again, to avoid condensation and blow-by. Your car has lasted this long; it’s now all about making it last even longer.