Regular oil changes are part of being a classic car owner. You may know how to change your oil; but do you really know what the correct oil is for your classic car? Let us first discuss what does all that writing on the label really means. Making the right choice in engine oil may save your engine from improper wear and possible damage.
SAE Motor Oil Meaning
In simple terms, SAE stands for “Society of Automotive Engineers.” This group designed the viscosity coding system for motor oils.
In fact, the SAE was founded by Henry Ford and Andrew Ricker back in 1905. Originally, it was meant to be the organization for automotive engineers working around the country, but it did not take long for the role to expand.
By 1916, SAE had added tractor and aeronautical engineers to the group and quickly formed into the group it is known as today. By the end of World War I, SAE had taken on an educational role, ensuring industry standards.
In fact, SAE standards go beyond oil viscosities. The group oversees the automotive industry but also has a part in aerospace, petroleum, trucking and more.
Its main role is to ensure consistency across the market. For example, the 5W40 motor oil that you enjoy in Ohio will be the same that you would buy in India. Without this standard, motor oil would vary wherever you were, causing the cost to also rise.
The SAE is responsible for maintaining over 1,600 practices and standards. While the SAE cannot enforce the law, the National Highway Traffic Safety Administration (NHTSA) has placed the SAE in the documentation that states the federal safety agency’s standards and rules. This is also true in Canada, where Transport Canada is responsible for setting guidelines.
What is Oil Viscosity?
Oil viscosity measures how long it takes the oil to flow through a particular container at specific temperatures. When the oil contains a higher viscosity, it takes longer to flow versus oil with a lower viscosity.
Typically, motor oil is rated with a number, XW-XX. For example, you will notice that motor oil is listed as SAE 5W-30, SAE 10W-30 or SAE 10W-40. Since we have already looked at the meaning of SAE, it is time to examine the other aspects of the formula.
The letter “W” stands for “Winter.” Many people assume that it means “Weight,” but that is not the case. The number located right before the W shows how the oil flows when at 0 degrees Fahrenheit. The lower this number is, the less likely the oil is to thicken when the temperatures get cold. In areas that are consistently cool, a 0W or 5W motor oil tends to perform the best.
After the “W,” there are two other numbers. These indicate the oil viscosity rating when operating at 212 degrees Fahrenheit. Basically, this number shows how fast the oil thins out when operating at higher temperatures. In this example, the 10W-30 motor oil and 10W-40 oil are going to function the same in colder weather, but the first is going to thin out faster when the temperatures rise.
Viscosity is the resistance to flow of a fluid. Engine oil viscosity grades are based on a scale developed by the API (American Petroleum Institute) lubricant organization. The values are defined in a specification known as API 1509 and are based on the resistance the oil gives to flowing at two different temperatures – cold and high temperature. The measurement of viscosity at high and low temperatures are properties of multi-grade oils. Years ago, most vehicles used one viscosity grade oil in the summer and a different viscosity grade oil in the winter. But as motor oil technology advanced, additives such as viscosity index improvers allowed for the use of the same grade of oil year-round.
The low temperature viscosity of the oil is a measurement that simulates starting a car on a cold winter day. That value has the letter “W” after the number and has a dash after the W. For example, if the oil is a 5W-30, the 5W part describes the viscosity of the oil at low temperatures. The lower the number, the faster the oil will flow at vehicle start up.
The high temperature viscosity is the number after the dash and is related to the viscosity of the oil as it is moving around your engine after the car has warmed up and is at normal engine temperature. In the 5W-30 example, the 30 defines the viscosity of the oil at normal engine temperatures. Again, the lower the number, the lower the viscosity of the oil and the faster the oil will move around the engine.
As an example, let us compare 5W-20, 5W-30, and 10W-30 motor oils. A 5W-20 and 5W-30 will have remarkably similar if not equal viscosity at lower start-up temperatures. But as the engine heats up, the 5W-20 will move with less resistance than an 5W-30. Less resistance results in improved fuel economy but the oil is not as thick and forms a smaller layer of protection between metal surfaces. If we compare a 5W-30 and a 10W-30, they will behave very similarly as the engine heats up, but at start-up, the 5W-30 will provide less resistance and start easier than the 10W-30. The 5W-20 will have a lower viscosity and provide less resistance than the 10W-30 at both start-up and normal engine operating temperatures.
In the past, it was common for vehicles to require higher viscosity oils such as 20W-50’s, 10W-40’s and 10W-30’s. But as engine technology has advanced over the years, the size of engines and pathways in engine that oil flows through have gotten smaller and thinner. This has led over time to motor oil viscosity decreasing – currently 5W-30 and 5W-20 are the most popular grade and 0W-20 is the fastest growing grade. These lower viscosity motor oils are needed to move through the thin engine pathways to protect and clean metal surfaces. Lower viscosity motor oils also result in better fuel economy.
Types of Motor Oil
Conventional Motor Oil
Back in the day, conventional motor oil was all that was available. It is the purest form of oil, containing no additives.
It is also the cheapest and easiest to find. While the oil follows SAE standards, it will require changing more frequently and does not provide high-performance protection.
Premium Conventional Motor Oil
There’s truly little difference between standard conventional and premium conventional oils. In fact, you will find the same 5W-30, 10-30 and other designations available. Additionally, these oils do not contain any additives.
Typically, these oils are pushed by car manufacturers as being better than conventional, but that is not typically the case. However, they can be used for most light-duty vehicles and often cost less than synthetic oils.
High-Mileage Motor Oil
If your vehicle contains more than 75,000 miles, you want to take extra steps to protect the engine. That is where high-mileage motor oil comes into play.
In some formulas, seal conditioners have been added. This formulation ensures more protection for the engine that is starting to wear out. You will find that these high-mileage oils often cost more, but if it keeps the engine running longer, it is well worth the expense.
Synthetic Motor Oil
Full-synthetic oil is designed to provide better performance and protection. Special additives are included for a variety of purposes, from cleaning out corrosion to lubricating the seals better. Each formula is made differently but must still adhere to SAE standards.
Synthetic oil will cost the most of all other options. However, you can push the vehicle longer without an oil change because of the special formulation.
Synthetic Blend Motor Oil
For most modern vehicles on the road, this type of oil is the preferred option. Basically, synthetic blends provide some of the benefits of full synthetics but are also mixed with some conventional oil to keep the cost down.
Each formulation contains its own additives, so research will be required to find the appropriate option for your vehicle. However, you should be able to go longer between oil changes than you did with conventional oil.
Finally
It is important to understand where to start with motor oil before changing your classic car’s engine oil. Every engine has certain needs as to the type of oil to be used so just selecting a modern synthetic oil may not be the best choice for the proper operation of your classic car’s engine.
