Do Older Cars Need Different Oil?

The evolution of engines and motor oils over the past century has significantly impacted how we care for our vehicles. While modern cars and engines benefit from thinner, more precise oils, older models often require specialized solutions to ensure optimal performance and longevity. This article explores whether older cars need different types of oil and why.

Evolution of Cars and Engine Oils

Historically, very old cars used single-weight oils such as 30 weight, whereas multi-weight oils like 10W-30 became standard around World War II. In the past thirty years, advancements in automotive design have led to closer engine tolerances, making it common to find oils as thin as 5W-20 and 0W-20. The age of a car in years is irrelevant; instead, the amount of mileage, type of engine, driving frequency, and conditions are the most significant factors.

For example, a 302 V8 with 130,000 original miles, driven frequently at high speeds with A/C on, requires a pure synthetic oil. This is because the engine tolerances and performance demands are quite high. Conversely, a car driven once a week at low speeds in a temperate climate could use a semi-synthetic oil, which would be more than adequate.

Oil Requirements for Older Cars

Older cars with flat tappet camshaft lifters require a higher zinc and phosphorus content in the oil to combat wear and tear. Modern cars, with roller camshafts, typically do not need as much of these additives. Flat tappet camshafts require more lubrication to prevent wear on the cam lobes, hence the need for higher zinc dialkyl dithiophosphates (ZDDP).

ZDDP, also known as Zinc dialkyl dithiophosphates, adhere to metal and act as a sacrificial wear surface. If any surface scuffing occurs, the ZDDP gets damaged, rather than the metal itself. This ensures the longevity of the camshaft. However, ZDDP is a catalyst poison for catalytic converters, and modern oils are designed to have lower ZDDP levels to meet emissions standards.

Options for Older Cars

For older cars that utilize flat tappet camshafts, the following options are available:

Heavy-duty engine oil: These oils still contain ZDDP and are suitable for diesel engines. Hot rod or older car oil: These oils advertise their zinc and phosphorus levels to meet the requirements of older engines. Synthesis supplementation: Supplementing the oil with ZDDP additives. Modern oil: Accepting the risk of reduced camshaft and catalytic converter lifespan with modern oils.

If your car is not catless and you notice oil burning, these barriers will impact both the catalytic converter and the camshaft. The ethical decision is to either replace the engine to stop burning oil, thus addressing both the catalytic converter and the camshaft concerns. However, this solution is not always practical or economical.

As an alternative, some owners opt for higher ZDDP content in their oil, understanding the trade-off between camshaft and catalytic converter lifespan. Ultimately, the choice depends on the owner's priorities and circumstances.

Conclusion

Older cars with flat tappet camshafts require specialized oils to maintain engine health. Modern oils, while more environmentally friendly, may not provide the necessary lubrication for these engines. Understanding the unique needs of older cars is crucial for ensuring both performance and longevity. Whether through careful oil selection, incorporation of additives, or engine overhaul, the goal remains to preserve these valuable and vintage mechanical wonders.