SAE 30 Vs 10w30: What’s the Difference?

If you’ve ever been confused about the difference between different types of motor oil, and specifically SAE 30 vs 10w30 grades, then worry no more because we’re going to help you out. It can be confusing trying to figure out which type of oil to use when you’re checking out at the store because there are all sorts of numbers written on the label that can quickly make your head spin. But it’s important not to get too bogged down by this because understanding how each grade of oil works is crucial to running a car engine effectively. So let’s take at the terms SAE 30 and 10w30, and see whether they have any difference.

So, SAE 30 vs 10w30, what’s the difference? The main difference between SAE 30 and 10w30 is that 10w30 is a multigrade oil while SAE 30 is a single-grade oil. SAE 30 motor oil is only used for warm temperatures and 10w30 motor oil maintains its viscosity in both warm and cold temperatures. It means that SAE 30-grade motor oil cannot be used in the engine if you’re driving a vehicle in colder temperatures. At the temperature of 212°F, both SAE 30 and 10w30 motor oils will perform in a similar fashion as their hot temperature viscosity grade is the same. If the temperature goes below 0 degrees Celsius, SAE 30 oil will become reasonably thick, due to which it will not flow through engine oil passages. As a result, you will hear a sharp knocking sound on the cold startup. So, in short, the cold ratings of SAE 30 and 10W30 engine oils are different, while the hot viscosity rating is the same.

If you look at the SAE 30 engine oil equivalent chart below, you can see that the motor oil of 10w30 rating can operate below the freezing point i.e. 0 degrees Celsius, while SAE 30 motor oil can only maintain its viscosity and fluidity above the freezing point.

SAE 30 engine oil equivalent chart

Bonus Read: Best motor oil for 3.5 Ecoboost

What is Viscosity?

Viscosity is defined as the ability of a fluid to resist shear forces between the layers of the fluid. A higher viscosity number means more resistance to flow and a lower viscosity number means less resistance to flow. SAE determines the kinematic viscosity of engine oil by passing it through an orifice at 100°C. If the oil is thicker, it will experience more resistance and time to flow through an orifice.

SAE has developed two separate viscosity measurements:

  • Hot-temperature viscosity
  • Cold-temperature viscosity

High-Temperature Viscosity

It is also called kinematic viscosity which is measured at 212°F. Its unit is cSt or centistokes. This viscosity is an indicator of how easily a motor oil flows through the different parts of the engine.

Cold-Temperature Viscosity

It is also called the absolute viscosity of engine oil at colder temperatures i.e. below 0°C. Its unit is cP or centipoise. It is further divided into two types of viscosities:

  • Cold-cranking viscosity
  • Cold-pumpability

Cold-cranking viscosity of engine oil is measured between -5°C and -35°C temperatures. It mimics the viscosity of the oil when it flows through the crankshaft journal bearing during startup in cold winter. This viscosity indicates that the oil has been sufficiently thinned to allow it to enter the bearing at cold temperatures so that the engine can be cranked over (crankshaft is rotated) fast enough to start under extreme cold ambient conditions. If the motor oil is quite thick on a cold startup, it will offer a very high resistance to the crankshaft of the engine.

Cold pumpability is the resistance engine oil offers to the oil pump when it starts pumping the oil from the oil pan to the engine after a cold startup. If the viscosity of motor oil is too high at colder temperatures, the oil pump will be unable to supply the oil to the engine. The cold pumpability of oil is determined between -15°C and -45°C. To qualify for a particular viscosity weight classification, the pumpability of motor oil must not exceed 60,000 cP for a designated temperature.

How Does Viscosity Affect Engine Oil?

In engine oils, viscosity refers to the thickening agent or fluid that helps keep engine oil circulating around inside the engine. In general, the viscosity helps to ensure there are no cavities inside the engine, which could cause damage to the engine.

Engine oil should have sufficient viscosity at cold starting temperatures so that it can be pumped and delivered to the engine. At a cold start, the oil needs to be viscous enough to prevent pump cavitation, but too high of viscosity causes the engine to run hot due to poor oil flow.  High viscosity is required in warm running conditions, which allows for lubrication and reduced wear.

What is SAE 30 Equivalent to?

SAE is the oil viscosity scale developed by the Society of Automotive Engineers. SAE J300 standard has specified the viscosity coding system for motor oils for efficient engine operation in different temperature conditions. SAE 30 grade motor oil can be equivalent to the 10w30 if the operating temperature is above 100°C as both SAE 40 and 10w30 motor oils have the same viscosity i.e. 30 while they are hot.

Also, do note that SAE 10w30 and 10w30 are the exact same motor oils formulated by the SAE. So, don’t get confused about that as people generally use the 10w30 term in daily life when talking about the viscosity grade of the motor oil. Otherwise, both SAE 30 and10w30 motor oils are assigned viscosity grades by the “Society of Automotive Engineers” so the viscosity grades of motor oils manufactured by several companies should be the same. That is, the 5w30 viscosity you get from Havoline engine oil is equivalent to the 5w30 viscosity you get from the Castrol motor oil.

Is SAE 30 the Same as 10w30?

SAE 30 motor oil is not exactly the same as the 10w30 motor oil. SAE 30 is single-grade motor oil, while 10w30 is multi-grade motor oil which makes it suitable for the varying temperature ranges. 10w30 starts out thinner during cold cranking of the engine so that it offers the least resistance to the oil pump and crankshaft at colder temperatures. As soon as the engine heats up, 10w30 motor oil gets thicker.

Also Read: 5w30 vs 5w20

10w30 oil is engineered to perform as a 10-weight oil at cold temperatures (during engine startup), and a 30-weight oil when the engine temperature goes above 212°F. 10w30 oil has more additives and modifiers than SAE 30 oil so it can maintain its flowing characteristics in both colder and warmer temperatures. The quicker the oil flows on a cold startup of the engine, the less will be the dry running of the engine. Less dry running means that there will be much less engine wear.

Multigrade motor oils follow two viscosity indexes, followed by two numbers. In 10w30 motor oil, ‘W’ stands for the winter viscosity. The number on the left of W in the oil viscosity grade indicates the cold-temperature viscosity index, while the number on the right of W in the oil viscosity grade refers to the high-temperature viscosity (In Summer Season). The lower the cold viscosity index, the better will be the engine oil’s flow at colder temperatures.

Without specifying the temperature at which the viscosity of engine oil is measured is meaningless as the viscosity of the oil is directly related to the temperature. SAE measures the hot viscosity of motor oil at the temperature of 100°C/212°F.  So, in SAE 30 and 10w30, ’30’ is the warm viscosity index assigned to the oil when it was tested at 100°C. The higher this number, the thicker will be the oil at 100°C, and the better it will provide protection to the engine against wear.

So, the maximum hot temperature viscosity of both SAE 30 and 10w30 motor oils at 100°C is 12.0 cSt, and the minimum viscosity is 9.3 cSt. The cold temperature at which the cold pumping of 10w30 motor oil is 60,000 cP is -30°C. The cold-cranking viscosity of 10w30 must not be greater than 7000 cP at -25°C to carry the 10W viscosity label.

As far as the performance of the engine is concerned, I went through the two case studies in which SAE 30 and 10w30 engine oils were used to notice any difference. It was found that the 10w30 engine oil showed a slight improvement in the fuel economy (MPG) of the engine. Moreover, bearing wear was lower with the SAE 10w30 grade motor oil as compared to the SAE 30-grade motor oil.

The reference to both case studies are given below:

  • https://www.jstor.org/stable/44564396
  • https://www.jstor.org/stable/44547333

What is SAE 30 Oil Used For?

SAE 30 oil was recommended to use in the older classic cars with high tolerances and in lawn mowers. SAE 30 is affordable motor oil, which is ideal to be used in warmer temperatures. Compared to the 10w30, SAE 30 oil has a bit higher viscosity, due to which it is a bit thicker and performs better until the engine temperature reaches 100°C.

In lawn mowers, people still use SAE 30 and save their money by not using 10w30 because the lawn mowers are supposed to be used in only summers. So, using 10w30 in the lawn mowers will not have a significant effect on their performance. It will only cost you extra money. 

Also, small engines like lawn mowers do not have very tight tolerances like the tight tolerances of the automotive engines. So, if you use 10W30 oil in a quite older lawn mower, it will not be able to provide sufficient lubrication as the 10w30 will be thinner than the SAE 30 oil below 212°F temperatures.

Furthermore, most lawn mowers are supposed to be run at steady RPMs i.e. they run at full throttle all the time, unlike the automobile engines that operate in a range of RPMs. Automobile engines first start at idle, and then slowly rev up. It means 10w30 in automotive engines starts getting thicker as their speed increases. But in lawn mower engines, the low viscosity of the oil at the full operating speed can cause different issues like blowing up the seal. 

However, make sure to check the owner’s manual of the lawn mower first to check whether you should use single-grade oil or multigrade oil.

Can I use 10w30 Instead of SAE 30 in My Generator?

Yes, you can use 10w30 instead of SAE 30 motor oil in the generator. But, if you are running an air-cooled generator in the summer, 10W30 motor oil will break up molecularly more easily as compared to the SAE 30 motor oil. Some manufacturers of generators mention in the owner’s manual that you can use 10w30 in the generator in temps up to 40 or 80°F.

Can I Mix SAE 30 with 10W30?

You cannot mix SAE 30 oil with 10w30 motor oil as SAE 30, being a single grade oil, cannot be mixed with multigrade motor oils like 10W30. Mixing the two motor oils can also result in voiding your vehicle’s or equipment’s warranty.