5W-30 VS 10W-30

5W-30 and 10W-30 oils perform similarly when the engine is running, typically at around 212°F (100°C). At this operating temperature, there is almost no difference between the two oils. However, the distinction lies in their viscosity characteristics at lower temperatures. 10W-30 oil is thicker when the engine is cold, which can affect its flow properties during startup and initial engine warm-up.
API (American Petroleum Institute) guidelines suggest using 10W–30 oil if you expect the outside temperature to stay above 0°F (-18°C). In regions where temperatures frequently drop below this threshold, it’s recommended to use 5W–30 oil. This ensures proper lubrication and protection for the engine, especially during cold starts when most engine wear occurs.

5W30 vs 10W30 when the engine is running:

Engine oil viscosity indicates how easily the oil flows at different temperatures, ensuring proper lubrication and protection for the engine’s components. Shown in the video are 5W30 and 10W30 engine oils in tubes at 100°C (212°F). A steel ball moving from top to bottom indicates the thickness or viscosity of the oil. At 100°C (212°F), the viscosity or resistance to flow is almost the same for both 5W30 and 10W30.

The number 30 in both 5W-30 and 10W-30 indicates the SAE viscosity at 100°C (212°F). That is the operating temperature of an average engine. The number before “W” (5W-XX and 10W-XX) tells the SAE viscosity of the oil when it is cold. W indicates winter or cold and that’s why it is shown here in blue color.

In the example above, 5W-30 has “SAE 5” viscosity and 10W-30 has “SAE 10” viscosity (5W and 10W) when cool. A higher SAE number means that the oil is thicker or has a high viscosity. SAE 10 is thicker than SAE 5, and similarly, SAE 40 is thicker than or has a higher viscosity than SAE 30. Check the SAE Viscosity chart called SAE J300 standard.

So both the oils 5W30 and 10W30 have the same viscosity (SAE 30) when your engine is running, and will perform in the same way. However, the 10W30 oil will be thicker (higher viscosity) than the 5W30 when it is cool.

“W” relates to winter or cold

Shown in the video are tubes with 5W-30 and 10W-30 lubricants. Both tubes with the steel ball were refrigerated at -18°C for half an hour. Air bubbles are trapped in the test tubes because of the low temperature. The thickness of 10W-30 is much higher, as shown in the video demonstration.

Which is better?

In modern car engines, it’s important for the oil to have good flow characteristics at startup, which means it needs to be thinner. During startup, when the engine is cold, the oil needs to quickly reach all critical engine components to provide lubrication and reduce wear. It’s widely acknowledged that a significant portion, often estimated around 80%, of engine wear occurs during startup, particularly during the warming-up phase when engine components are not yet at their optimal operating temperatures. 5W30 oil has the same viscosity at 100°C but is thinner when cool. 5W30 is usually a semi-synthetic or fully synthetic lubricant. The only problem with 5W30 is NOACK (evaporation tendencies of a lubricant (engine oil) at high temperature).


In regions experiencing colder temperatures, 5W-30 is preferable for its better cold start performance, which can mitigate engine wear. However, in milder climates, or where temperatures rarely dip below freezing, 10W-30 may perform just as effectively without compromising engine protection. Choosing between 5W-30 and 10W-30 should be guided by the specific operating environment and manufacturer recommendations.

According to API motor oil guide [1], If you are using 10W30, you can safely switch to 5W30 (in car engines). 5W30 is thinner than 10W30 when cold. (you must follow the manufacturer’s recommendations). However, switching from 5W30 to economical 10W30 is not always recommended. You can use the 10w30 if the lowest expected outdoor temperature is always above -18°C. I am using 5W40 for my car instead of 15W40. It is a recommended lubricant along with 15W40 by the engine manufacturer, even though I am driving in a hot climate in the gulf region. 5W is a synthetic lubricant having better oxidation resistance and longer drain intervals.

Can I use 10W-30 instead of 5W-30?

The only reason to choose 10W-30 is the price. Otherwise, 5W-30 is superior to the 10W-30 for car engines. Better select synthetic 10W-30. You can only switch to mineral 10W-30 if the lowest expected outside temperature is above -18°C (0°F). Always follow engine manufacturer recommendations.

Can you use 5W-30 instead of 10W-30?

Both 10W-30 and 5W30 have the same viscosity at the operating temperature of the engine. 5W-30 is usually synthetic and superior to 10W-30. 5W has lower viscosity when cool and is considered better for the car engine during engine start. For high-power diesel engines, follow manufacturer recommendations because of higher NOACK in 5W.

Is 10W-30 thicker than 5W-30?

Both 10W-30 and 5W30 have the same viscosity at 100°C (212°F), it is the operating temperature of an average engine. But 10W oil is thicker or has higher viscosity when cool.

What does the “W” stand for in the SAE viscosity grades?

W” stands for winter, for example in 5W30, the lubricant  has SAE 5 viscosity when cold and SAE 30 viscosity when the engine is running. There are 2 sets of numbers in 5W30 separated by a dash(-). The number 30 [3] relates to the viscosity or thickness of the oil when it is at 100°C. It is considered a working temperature for the average engine. The “W” means winter and 5W relates to how the oil performs when it is cool. So 5W30 is SAE 30 viscosity when at 100°C and SAE 5 viscosity when cool.


(1) Motor Oil Matters by api.org

(2) SAE Viscosity Grades.

(3) SAE J3oo viscosity grades for engine oil

22 Responses

  1. Good basic information comparing apples to oranges here. First, compare 5W-30 hydrocracked synthetic to 10W-30 hydrocracked synthetic, NOT dino 10w-30. And please supply the viscosity temperature graphs superimposed on each other so readers can see the actual differences in both synthetic 5W-30 and synthetic 10W-30 as most will find very little to no difference unless at very cold temperatures of the graph. You have got folks here scared to death if they don’t buy 5W-30 viscosity motor oils. Cold start might account for more engine wear than other kinds of wear, yet where two multi viscosity oils that are virtually the same viscosity at ambient temperature, 5W-30 isn’t going to make an engine last any longer.

    1. Addressing your insightful points requires a nuanced understanding of motor oil viscosities, their performance across temperature ranges, and the practical implications for engine wear, particularly during cold starts.

      A 5W-30 oil is designed to flow more easily at lower temperatures than a 10W-30, while both oils are intended to offer the same protection at operating temperature. Cold starts are indeed critical because most engine wear occurs during this time. Oil needs to reach all parts of the engine promptly to minimize wear. In colder climates, or where temperatures can drop below zero, the initial fluidity of the oil becomes crucial. A lower winter viscosity (e.g., 5W-30) ensures that the oil moves more quickly through the engine, providing faster protection compared to a higher winter viscosity oil (e.g., 10W-30).

      When comparing synthetic oils of different viscosities, it’s essential to focus on their performance characteristics. Synthetics generally offer better performance across a wider temperature range than conventional oils (“dino” oils), including improved flow at cold temperatures and better stability at high temperatures. For 5W-30 and 10W-30 synthetic oils, the key differences emerge at lower temperatures, where the 5W-30 oil will circulate more readily, potentially offering superior protection during cold starts.

      Presenting viscosity temperature graphs for both 5W-30 and 10W-30 synthetic oils could indeed clarify their similarities and differences across temperature ranges. While at ambient and high temperatures, their viscosities converge, highlighting the significant variance at cold temperatures which is where 5W-30 has its advantage. This visual comparison would illustrate why 5W-30 is often recommended for colder climates, not necessarily implying a universal superiority over 10W-30 in all conditions.

      Choosing between 5W-30 and 10W-30 synthetic oils should be guided by the specific operating environment and manufacturer recommendations. In regions experiencing colder temperatures, 5W-30 is preferable for its better cold start performance, which can mitigate engine wear. However, in milder climates, or where temperatures rarely dip below freezing, 10W-30 may perform just as effectively without compromising engine protection.

      In conclusion, while 5W-30 and 10W-30 synthetic oils may offer similar protection at normal operating temperatures, the choice between them should consider the potential for cold starts and the corresponding engine wear. The emphasis on 5W-30 for colder climates is based on its superior low-temperature flow characteristics, ensuring rapid lubrication during the most critical phase of engine operation.

  2. 5w-30 is not “superior” to 10w-30. maybe if you live in alaska. 5w contains more improvers than 10w, which means less lubricants. the reality is that 5w is just thinner oil, even when hot.

    1. There is a misconception that 5W30 oil necessarily contains more Viscosity Index Improver (VII) than 10W30 oil. It’s more nuanced than that.
      While a conventional 5W30 oil might use more VII than a conventional 10W30. This isn’t always the case. A synthetic 5W30 might rely less on VII to achieve the desired viscosity grade. Synthetic base oils naturally have higher inherent viscosity indexes than conventional oils. This means they may require less VII to achieve a desired multi-grade rating.

      Approved formulation of 5W30

      (DI) Additive Package 8.64 %
      Viscosity Index Improver 5.8 %
      PPD 0.15 %
      Group III 4 and 6cSt Blend 85.41 %

      Approved formulation of 10W-30

      DI Package 8.64 %
      VII 5.90 %
      PPD 0.15 %
      Group II Base oil Blend Remaining

  3. I bought oil for my car thinking it took 10w 30 for some reason but on the filler cap it says 5w 30 and i was wondering will this damage my car it don’t uselly get below zero sometimes not much we get some negative numbers a few times during the winter but on the back of the oil container it says it meets the Chrysler standereds which i have a 09 Chrylser Sebring i don’t think this will harm i know in the winter time it may take longer to warm up the oil

  4. Troy Bilt super bronco 50 xp riding mower says use 10w30. Ok or not to use 5w30 in northeast Texas? Gets 100+ here in summer, and usually not colder than 30 for long periods (plus not usually running mower in the winter…). Thanks.

    1. Mary, generally it will not affect anything regarding the standard running of your motor – the second numbers are the viscosity (thickness) of the oil at running temperature (about 100°c/212°F).
      The first number is the viscosity at startup of the engine. Any engine will be at running temp pretty fast though so as long as the recommended startup grade of oil is thin enough for the engine to kick along happily till it’s warm enough, by time it’s warmed up the oil won’t be any difference anyway…
      So even in Texas, once the engine being used reaches 212°F running temp, the oil you want to change to will be the same thing really 👍

    1. 5W-30 and 10W-40 are different lubricants. In my opinion you are safe with 10W-40 if outside temperature in your area is above zero degrees. If you are looking for 5W, it is better to use 5W-40. 5W-40 has same viscosity but more fluid during cold engine start.

    1. It depends and you must follow manufacturer recommendations. As a guide, synthetic 10W-30 may run 10,000KMs or more if recommended by the manufacturer.

  5. Hello my name is Michael I have a question I have a 2004 silverado Z71 I’m using Castrol 10w40 high mileage because I have 265.000 can i go back using 5w30 Castrol Edge full Synthetic

  6. Hello

    I will like to make an inquiry about your line of Motor Oil. I want to know if you have the below specifications available and also I will need a formal quote regarding it.

    I will be looking forward to get a quick response to this. Find below is the specification of the products being requested.

    1) 5w-30 Engine Oil….5ltrs (5qrts) Synthetic …..3000 Units

    Stay Safe

  7. If you are using 5W-40 instead of 15W-40, what are the benefits/drawbacks of using 5W while driving in hot climate like gulf? Are you following manufacturer recommendations?

    1. 5W lubricants are mostly synthetic, Synthetic base stocks have superior performance than minerals base oils. The only drawback for 5W is high noack value that is not a big problem for car engines. Yes 5W is recommended by the engine manufacturer along with 10-40 and 15W-40. My car is now 6 years old and at 205,000 km, it is like new.

    2. Can i use 10w30 synthetics instead of normal 5w30 .lowest temperature here 19C degree .and high temperature of 40C

      1. Yes, you can use fully synthetic 10W-30, But you still have to check owner’s manual to verify the recommendations by the engine manufacturers.

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