Is Synthetic Motor Oil Bad For Old Cars?

Summary by Krater

An engineer from Engineering Explained answers four common questions about using synthetic motor oil in older cars, exploring whether synthetics cause leaks, whether thicker oil is needed for oil-consuming engines, and when high-mileage oils are useful.

From the video

Answers: Can you use synthetic motor oil in older cars?

• Synthetic motor oil in older cars
• Oil seal compatibility
• High-mileage motor oil benefits
• Engine wear and oil viscosity

What it concludes

• Synthetic oils can be used safely in older cars without causing issues.
• Early synthetic oils caused engine seal swelling due to ester concentration, but modern synthetic oils are engineered to be seal-compatible.
• Switching to a thicker oil may prolong the life of an engine with increased bearing clearances due to wear, but it will not fix engine wear or oil leaks from failed seals.
• High-mileage motor oils include seal-conditioning agents that help recondition hardened or shrunk engine seals and reduce oil consumption in aging engines.