5W-30 VS 10W-30

5W30 and 10W30 lubricants have the same viscosity at the operating temperature of the engine. That is usually 100°C (212°F) when the engine is running (in an average engine). However, the 10W30 oil will be thicker when it is cold. As per API recommendations (1) for car engines, you can use 10W30 oil if the maximum expected outside temperature is above -18°C (0°F). If you are living in an area where the outside temperature can go below zero; It is better to use 5W30. Always follow the engine manufacturer’s recommendations.

5W30 vs 10W30 at 100°C:

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 exactly 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, we need the oil to be thinner at the time of startup. Most experts agree that 80% of engine wear occurs during  startup (warming-up) the engine. There is a problem with the thicker oil when the engine is cold. We need the oil to be thinner at the time of starting the engine. The lubricant must reach all parts of the engine right away. However, the problem with thicker oil is that the oil’s resistance to flow is high. Hence, the oil will not reach all around the moving parts of the engine when you turn the key. 5W30 oil has the same viscosity at 100°C but is thinner when cool. 5W30 is always a synthetic lubricant. The only problem with 5W30 is NOACK (evaporation tendencies of a lubricant (engine oil) at high temperature).


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. According to API motor oil guide [1], you can use the 10w30 if the lowest expected outdoor temperature is above -18°C and you are following the manufacturer’s recommendations. 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

20 Responses

  1. 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

  2. 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

  3. 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.

  4. 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

  5. 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

  6. 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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