tl;dr version:
accidentally bought and used monograde petronas mach 5 SAE 40 in iswara.
what are likely adverse effects of this?

i recently serviced my old iswara (1998). I usually buy my own engine oil coz my mechanic doesnt stock the brand of oil I want.
in the past, i always use magnatec 10W40 for this iswara but my mechanic recently told me its too thin to protect my old engine so he recommended i switch to mineral oil - petronas mach 5 specifically.

so i went and bought a petronas mach 5 engine oil. since this is the first time im buying mach 5, i didnt really check properly what i bought.
turns out, i accidentally bought the monograde version, SAE 40. i only discovered it while i am preparing to buy another canister for my next service.

to be honest, i am quite happy with the oil, the car started fine and the engine runs cooler and smoother with less vibration than before which was a surprise to me. seems like a good move from magnatec to mach 5 monograde EO for an old magma engine.

but i am a bit apprehensive that my engine is not getting the protection it needs during morning starts. is this really a valid concern or is SAE 40 actually perfectly fine to use in Malaysia?

thanks for the feedback, guys.

and to further confirm that its fine with technical data, i just found this chart below that shows SAE 40 grade oil actually has lower viscosity at 20 deg C than 10W40 grade oil at 10 deg C.

since the malaysian climate is between 22-32 deg C and 10w40 oil is designed to work in temps as low as -30 deg C, i can safely say that monograde SAE 40 is perfectly fine to use in malaysia.

I'll probably stick to using monograde for my iswara coz its cheaper and works great.



This post has been edited by homicidal85: May 25 2022, 10:23 AM

after making this discovery, i feel like i have been cheated all this while. i live in malaysia. i dont need multigrade bullsh*t that gets thinner faster. i should have been using cheaper, better monograde on all my cars all this while.

UPDATE: after 3 months using monograde oil, my car takes 2 cranks to start in the morning. I think initially it was perfectly fine because there was still some residual EO (castrol magnatec probably was still sticking to the pistons and cylinders) but over time, the magnatec wore off. So, the monograde oil isnt fluid enough for a one time crank during early morning. But once it starts, it works fine. The engine still runs cooler than when i used multigrade oil.

if your engine is new, I wouldnt recommend using monograde oil just to make sure you have proper protection during the early morning cranks. but for old cars which might burn multigrade EO, its probably a better choice to use monograde because it doesnt suffer from thermal breakdown as quickly as multigrade so there is overall less chance of damage to the engine.

IMO, its the best option for my iswara so I will stick to monograde for this car. multigrade oil tends to degrade quite fast in this car so it is a less reliable choice than monograde. i have googled and there doesnt seem to be any issues with cranking twice. cranking for long periods more than 10 times a day is when you start to see wear on the starter motor, flywheel and carburetor so I dont think my 2 cranks lasting 1 second each time would cause any significant issues.