Motor Oil Grades: Demystifying What They Mean

Each manufacturer has a specific recommendation or minimum requirement for the type of oil that a given engine will use. You may be wondering, what is the difference between different weights, grades, and viscosities? What is the difference between 5W-30 Y 10W-30? What do all these numbers mean? Can’t use oil in your car or does it really matter?

Cracking the Oil Code

The terms weight, grade, or viscosity are commonly used interchangeably and basically mean the same thing. They refer to the thickness or ease with which the oil flows. Using a multigrade 5W-30 Oil as an example, this type is widely used in millions of vehicles. The first number followed by “W” indicates the viscosity (or thickness) for cold weather temperatures. The “W” means winter. The lower this first number is, the less viscous or thinner your oil will be at lower temperatures. Although it may seem trivial, the number is of great importance.

When engines first roar after turning the ignition key, the oil pump tries to push oil from the bottom oil pan to the top of the engine, to lubricate all moving parts (such as pistons, camshaft, etc.) ) Cold starts are the moment of greatest wear imposed on the engine. The heavier (or thicker) the oil, the harder the oil pump will work and the longer it will take for the engine to receive the crucial oil lubrication it needs to prevent metal-on-metal friction when starting. So, it has 5W- the oil will flow faster and easier than a heavier oil that would have a higher number like 10W- Prayed 15W- oil.

The second number after “W” specifies the viscosity at high temperatures. The higher the number, the thicker the oil will be at the optimum temperature. In older cars, it was common to switch to different weights of oils depending on the season. It is a practice that is not so common today due to manufacturers building lighter engines and using different engine materials than in the past, it is always recommended to follow the manufacturer’s fluid specifications found in your vehicle manual.The use of a weight of oil than recommended will likely result in lower fuel economy or increased engine wear

Are there exceptions to the rule?

The occasional exception to the “follow manufacturer’s recommendations” rule comes into play when an engine has aged and when moving parts may have larger gaps between components. Thicker oils can sometimes improve performance and protection in such conditions, but for most vehicle owners, follow the vehicle manual’s specifications.

What do the manufacturers say?

Some manufacturers will list a range of different types of motor oil depending on the climate in which the vehicle will be used. A lighter oil is likely to be recommended for vehicles in arid southern areas, such as Scottsdale, Arizona, while a lighter oil may be better in colder climates, such as those found in Rapid City, South Dakota. Oil in South Dakota will obviously be subject to colder engine starting conditions during the winter months than oil in Arizona during the same time period.

What is straight oil versus multi-viscosity oil?

You should never use straight oil (SAE30, SAE40, SAE50, etc.) in a system designed for a multi-viscosity oil. Straight oils are used for smaller engines or older car engines made before multi-viscosity oils were created. Although snowmobiles, ATVs, and motorcycles have smaller engines than most passenger cars and trucks, straight oils should not be used in such vehicles. Even regular automotive oils may not be appropriate due to specific engine designs, such as two-stroke versus four-stroke engines.

Take care of the engine you depend on

Ultimately, using the proper grade of oil and changing your vehicle’s oil at prescribed regular intervals are two of the most important preventative maintenance tasks you can perform for your vehicle. Failure to do so can lead to oil depletion and ultimately cause the engine to seize. Most repairs related to improper or negligent handling of oil are preventable and expensive. It’s better to invest in good auto service practices now than pay a painful repair bill later. Knowing the right oil to put in your vehicle (and why) is a good first step in taking care of the engine you depend on.