The Difference Between Motor Oils: 10W30 And 5W30
Dear Master Tech Automotive,
What is the difference between 10W30 motor oil and 5W30 motor oil?
Signed,
Confused
Michael Searcy says:
In 10W30 oil, for example, the two numbers (10 and 30) mean it’s a “multiviscosity’ or “multigrade” oil that’s effective over a range of temperature. The first number, 10, is an index that refers to how the oil flows at low temperatures. The second number, 30, refers to how it flows at high temperature. The W means the oil can be used in a winter.
A popular belief is that 5W30 oils were to thin to protect vital engine parts when they get hot and 10W30 caused harder starting on those cold winter morings, but numerous studies have concluded there is essentially no difference between 5W30 oils and their 10W30 brand mates. There is no visable way to tell the difference.
A larger number of automakers now recommend 5W30 as the “preferred” oil and even identify 5W30 on the oil filler cap. However, in most cases the manufacture also provided a chart with various temperature ranges and the acceptable viscosity. In our region the temperature ranges usually allow the use of either 10W30 or 5W30. Most consumers in the state of Tennessee use the 10W30 because it is the most availabile and usually the least expensive, while maintaining quality and your manufacturer’s warranty.
The purpose of oil is to help protect the engine’s moving parts. But motor oil does much more than lubricate. It helps cool the engine, keeps it clean, prevents corrosion, and reduces friction to improve fuel economy. The worts mistake you can make is to put a single grade oil in an engine that was design to be run on a multigrade oil. Viscosity grade is important to the life of your engine, so be careful. Recommendations vary with the make, engine, and model year of the car, so check your owner’s manual and ask your mechanic for the proper grade of oil.
