I recently checked my wife's car and its maintenance record and saw that the agency has been replacing the engine oil with 20/50 during routine maintenance. We live in a tropical country where the temp never goes below 10 degrees Celsius, or above 40.

Previously I only used this grade (20/50) when doing maintenance on my motorcycles.

I plan on doing the maintenance in the future as it has aged to the point where it is no longer worthwhile letting the agency do it.

Should I continue with this, or switch to a 30 or 40 weight oil such as is recommended for this climate?

3 Answers 3


The 20/50 should be fine for the temperatures you mention - I used to use a 5/50 to cope with colder winter and summer motorway work and avoided having to change from a winter to summer grade etc.

Regular servicing and changing the filters will have greater effect than using an oil slightly close to the “edges” of its range - the oil performance is rated on “bands” so it’s not above x and it must be y...

  • I am getting a "burnt" smell and look from the dipstick. Would the higher grade give better performance? Commented Jan 4, 2018 at 21:19

one reason would be if you want to run a synthetic oil, most major brands don't even make "straight 30" or 40 synthetic. Do your service records indicate the brand/type of oil?

Also have you looked at the actual recommendation for your actual vehicle? They usually "recommend" some multi weight for all climates and "permit" a straight weight in warm climates.

  • I am not using synthetic. And as indicated, the service records show 20/50. I think the question has that. And Mazda does not provide sufficient info in their user's manual ie "do these maintenances at an agency". Thus, I am here. Commented Jan 4, 2018 at 20:42
  • I was suggesting the shop may have picked 20/50 because they used synthetic. I was asking if the paperwork indicated the specific brand and type (ie synthetic or not ).
    – agentp
    Commented Jan 4, 2018 at 21:26

...seems your question implies another: could the use of 20W50 oil in the tropics be detrimental...as opposed to straight-viscosity such as 40-wt or 50-wt?

In more than a few instances what the service provider will install is what it will have decided in its own economic interest to keep on hand, so the question could be: why did the tropically situated service department not keep or have in stock, say, the straight 40-wt or 50-wt?

Well, most likely it is more economical to stock fewer as opposed to greater numbers of oil varieties; and so, if it comes to a viscosity choice between single-weight and WinterSummer grades, the latter is preferable for two reasons:

  1. Because most new car manufacturers do NOT recommend single grade oils because cars must operate in tropical as well as temperate conditions, and
  2. Because lubricating with (in your case) a 20Winter50(summer) grade oil where winter never occurs is tantamount, in practical terms, to lubricating with a 50wt oil in ambient conditions never varying from such, in tropical climes, as typically requires or is compatible with 50-wt oil.

As for your own servicing, following the specified oil recommendation where available will do not harm.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .