10W30 vs 10W40: Engine Oil Viscosity Explained

10W30 vs 10W40

As a motorcycle or car owner, you must have basic information and knowledge about your vehicle’s engine oil, especially as it concerns its viscosity. How much time have you spared to know the difference between 10W30 and 10W40?

If you’ve not knowledge about the viscosity of your vehicle’s engine oil, here is a chance to have an insight into it, especially as we look into the 10W30 and 10W40 naming convention.

10W30 vs 10W40: Differences at a Glance

Detail: 10W3010W40
Weather: cold vs hotIdeal for cold-weather regionA perfect pick for hotter, warmer climates
Engine performanceMaintain optimum engine protection in a cold climateHelps to amplify engine heat in warm region
SpecsThins out very fastTakes time before it thaws
Resistance to climateMay not be able to prevent scraping of your engine’s metallic parts after some timesGiven its low heat generation, it is capable of preventing metallic parts of your engine to scrape.
ViscosityLower viscosityHas higher viscosity

10W30 vs 10W40

These are both multigrade oil that has the same ability in winter 10W. The difference is in their ability at higher temperatures. 10W30 will be thinner at a higher temperature than 10W40. If you live in a colder region, your machine will be better served with 10W30 oil and for a hotter region, you may want to opt for 10W40 engine oil.

There was a time when it was necessary to swap oils as the season changes, but with better formulation techniques and a better understanding of oil chemistry, all that is required is to understand the naming convention and you’d be able to choose an oil whose viscosity serves both situations.

Why Does Your Vehicle Need Engine Oil?

In machines, oil is used as a lubricant to reduce friction between moving parts. Therefore, it should be able to handle different temperatures to keep functioning appropriately as a lubricant.

Loosely, viscosity can be likened to thickness. Technically, viscosity is a measure of friction in a liquid. The more closely packed or the more friction that exists within the liquid particles, the more viscous the liquid is and the less friction internally in a liquid the less viscous the liquid is.

However, different types of oil behave differently at different temperatures, hence understanding the intricacies of viscosity to determine what oils are suitable in different situations.

Some types of oil clump up in cold temperatures and do not flow easily, making them unsuitable for cold temperatures. Conversely, in high temperatures some oils breakdown and become very runny and lose their ability to lubricate.

The balance is to find the oil that flows easily in cold temperatures and still retains its lubricating property in high temperatures.

This idea informs the naming convention of machine-grade oils. The Society for Automotive Engineering(SAE) is responsible for the naming convention and classification of oils. The ‘W’ stands, not for weight as assumed, but for winter.

Single Grade Oil vs Multi-Grade Oil

Before we break down these interesting sets of numbers let’s point out two different types of oils that exist. Single grade oil and Multigrade grade oil. Now it stands to reason that for cold temperatures, you would want to use oils that do not clump easily. 

One, that even in the dead of winter, would still flow appropriately to meet your engine’s needs. You would also want the type of oil that would not break down at high temperatures. Some oils are either good for either hot temperatures or cold temperatures. These are single grade oils.

Based on the SAE naming conventions, SAE 30 is thinner than SAE 40 and can perform better in colder situations than SAE 40, but SAE 40 can perform better in hotter situations than SAE 30.

However, what if we needed an oil that can perform optimally in both situations? Enter multigrade oil. This oil can flow easily at cold temperatures and resist deformation at high ones.

These types of oils can do this to varying degrees, hence the naming convention. SAE 10W40 represents a multigrade oil naming convention. The number preceding the W indicates its ability in winter and the number following the W indicates its performance in hotter temperatures relative to 212F or 100 degrees Celsius. 

Deciphering is complete.

Frequently Asked Questions

Q: Is 10W30 thicker than 10W40?

No. 10W40 would be thicker in cold weather but they serve just as well in cold temperatures despite their difference in thickness. What that means is that you won’t go wrong if you opt for either of the two engine oil grades. They will deliver the required viscosity your engine needs for an all-day smooth ride.

Is thicker oil ideal for a high-mileage engine? The direct answer to the question is yes. To improve the performance of your high-mileage engine, you need to use thicker oil. Besides, improving oil pressure in an older engine, slightly thicker oil is the best option to opt for. This kind of oil, which usually comes from a heavier base weight oil like 10W30 oil, will help to prevent your engine bearings from corrosion and rust.

Q: Can I swap one for the other?

If the only consideration is their performance in cold weather, then yes; you can always use one in place of the other to improve the delivery of your high-mileage engine in cold weather. However, it is best to follow the manufacturer’s recommendations. 

Final Thoughts

While most manufacturers have their recommended oils, it is sometimes best to follow the manufacturer’s recommendations. However, understanding this naming convention will serve as valuable information in making decisions as regards your oil needs in specific conditions. The difference between 10W30 and 10W40 engine oil will help you understand what type of season you should use particular engine oil. It will also help you make an informed decision about the type of engine your vehicle needs.