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My car is Suzuki alto japan 2017. According to the owner's manual, car manufacturer recommends 0w-20 or 5W-30 engine oil. But the previous owner has used 10w-30 oil. The average temperature of the area I live in is 27°C. Temperature ranges from 25 to 32°C (77 to 90°F). Does it matter if I use 10W or 5W?

I have read that less viscous oil tend to break under high temperatures. But a mechanic advised me to use 0w-20 since the engine is small and have very small clearance in engine parts.

Which oil is better for the engine life 0w-20 or 10/5w-30?

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  • I would stick with 5w30 in your temp range.
    – Moab
    Feb 13, 2019 at 16:36

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A lower viscosity is important in sub-zero temperature because oil can become so thick as to prevent the engine from turning over during a cold start. You live in a tropical environment (the 10W or 5W makes no difference), so I would think you would be better off following the manufacturer's recommendation.

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    One thing you don't mention, which is of concern for vehicles spec'd for 0W-20 oil. Manufacturers have gone to the "thinner" oils due to fuel economy. It takes less energy to push these oils around. To do this successfully, they must also use tighter bearing clearances. For these engines, while oil pressure is maintained (or even exceeded) with the heavier oils, it may not be getting the oil flow it needs.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Feb 12, 2019 at 13:26
  • New engines with tight clearances need the lower viscosity oils for sufficient flow volume over the bearing surfaces for cooling ; more or less what your mechanic said.
    – blacksmith37
    Feb 12, 2019 at 15:07
  • The manufacturer also recommends 5w-30 which is more viscous than 0w-20. What is the reason for recommending oils of two different viscosities for the same car?
    – pahan
    Feb 12, 2019 at 18:03
  • Since the less viscous oil tend to degrade more under high temperatures, isn't it safer to go with 5w-30 given the average temperature in my area
    – pahan
    Feb 12, 2019 at 18:09
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Your mechanic is correct. The only reason you should ever use thicker oil is if the engine is high-mileage and you are getting symptoms of pressure loss.

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  • Thanks for the answer. Should I immediately flush and change my oil to 0w-20 or is it safe if I switch to right oil from the next service
    – pahan
    Feb 12, 2019 at 18:06
  • i really don't think you'll hurt it. You may affect your gas mileage. the first # is the viscosity in cold weather and the 2nd in hot (multi-weight oil actually thickens as it warms up) so it shouldn't be an issue when cold as the first number represents freezing temps. so in your case the 0 to 5 doesn't even apply to you. The manufacturer recommends a 30weight so it should be safe. In the future though get the thinner oil.
    – John Lord
    Feb 12, 2019 at 19:28

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