Is 10W40 Superior for Older Cars with High Mileage?

When it comes to choosing the right motor oil for your vehicle, the advice in the owner's manual is often the best place to start. However, for owners of older cars with high mileage, such as a 2000 Chevrolet truck or a 1962 Buick V6 in an old Jeep, using a thicker oil like 10W40 may have its advantages.

Understanding Viscosity Ratings

The first digit in the oil's viscosity rating (like 10, 5, or 40) indicates the oil's viscosity while it's cold, while the number after the "w" (like 5, 10, or 40) represents the viscosity when the engine is running and warm. This is an important detail to consider when choosing the right oil for your engine.

Using 10W40 in Older Vehicles

Owners of older cars often experience issues with thin oil causing leaks or excessive burn-off. This is particularly true for engines with high mileage. In my case, the 2000 Chevrolet truck is specified to run 5W30, but I've always used 10W40, and with good reason. A thicker oil in these high-mileage engines tends to be less likely to leak or burn up.

The 2000 Chevrolet truck consumes around a quart of oil every 250 miles when using a thinner oil. Using 10W40 reduces this consumption, potentially saving money on oil changes and reducing the need for frequent top-offs.

Extreme Cases

There are, however, extreme cases where using a thicker oil is necessary. For example, my friend had a Volkswagen Golf whose engine was replaced. The high mileage and new engine combination required a thicker oil than what was originally recommended. This was necessary to maintain oil pressure, which dropped too low during idling in the thinner oil, causing warnings to go off.

Unless the engine is experiencing specific issues that necessitate a thicker oil, such as high-mileage problems or specific performance needs, the recommended oil from the manufacturer is generally the best choice. It has been optimized by the manufacturer to best suit the engine's design and ensure reliable performance.

Exceptional Cases

My 2000 Chevy and 2002 Grand Prix both still use 5W30 after over 200,000 miles. For the Jeep with a 1962 Buick V6, the 10W40 has worked well, but at hot idle, the oil consumption is a concern. This might require me to switch to a thinner oil or check for other issues like a faulty radiator, as I recently replaced it.

Conclusion

While the oil recommendations in the owner's manual should be the first point of reference, they are not always the one-size-fits-all solution for high-mileage vehicles. In certain cases, such as engines that experience frequent leaks or burn-off, a thicker oil like 10W40 can be beneficial. However, it's always wise to consult a professional mechanic or knowledgeable online community for specific advice tailored to your vehicle's needs.

Remember, the key is to prioritize the health and longevity of your engine rather than strictly adhering to the manufacturer's specifications. Whether you decide to stick with the recommended oil or experiment with a different type, always prioritize the well-being of your vehicle's engine.