5w30 or 5w40

[Petr]

Apparently hot weather doesn’t matter since thermostat will keep engine at certain temperature?

The thermostat tries to keep the coolant temperature at some temperature (e.g. 200F). However, as the ambient temperature increases the cooling performance decreases. The car cooling system is designed with some assumptions and the result is always a compromise between costs and performance. When the power output of the engine is high, the thermal output is also high. At high ambient temperatures, the cooling performance might be at its limits. In such a case, the ability to keep the oil temperature in a normal range might be assured only when the power output is sufficiently low. At high speeds (high thermal power output) the thermostat may be fully open and yet the oil temperature might be significantly elevated.

At much lower ambient temperatures I have observed that oil temperature increased from quite stable 200F (195F to 205F) to 260F (with peaks up to 275F) just by increasing the speed from 80 mph to 110 mph. I bet the thermostat tried to keep the temperature lower.

In Saudi Arabia ambient conditions, I would aim for a 5w40 or 0w40 or even 5w50 with approvals like Porsche A40 / C40 etc.

 

[Yukiwari]

The thermostat tries to keep the coolant temperature at some temperature (e.g. 200F). However, as the ambient temperature increases the cooling performance decreases. The car cooling system is designed with some assumptions and the result is always a compromise between costs and performance. When the power output of the engine is high, the thermal output is also high. At high ambient temperatures, the cooling performance might be at its limits. In such a case, the ability to keep the oil temperature in a normal range might be assured only when the power output is sufficiently low. At high speeds (high thermal power output) the thermostat may be fully open and yet the oil temperature might be significantly elevated.

At much lower ambient temperatures I have observed that oil temperature increased from quite stable 200F (195F to 205F) to 260F (with peaks up to 275F) just by increasing the speed from 80 mph to 110 mph. I bet the thermostat tried to keep the temperature lower.

In Saudi Arabia ambient conditions, I would aim for a 5w40 or 0w40 or even 5w50 with approvals like Porsche A40 / C40 etc.

thank you very much I appreciate your convincing answer

 

[Kalle.J]

Could it be ECU that is dialing back timing because of heat/pre-ignition high intakte temps etc.? That could make an audible difference.
Does not explain the difference between oils though.
Regardless continue with 40-50 viscosity oils. Maybe change watercooling-liquid and make shure thermostat opens fully.
Inspect radiatior fins from debris ?

 

[Yukiwari]

Could it be ECU that is dialing back timing because of heat/pre-ignition high intakte temps etc.? That could make an audible difference.
Does not explain the difference between oils though.
Regardless continue with 40-50 viscosity oils. Maybe change watercooling-liquid and make shure thermostat opens fully.
Inspect radiatior fins from debris ?

actually , it's time to change the radiator and fan. The car has been around for 8 years and 190,000 miles, the 5w40 make the engine quite at high speed

 

[Yukiwari]

After using the viscosity of 5w40 for a period of time, I noticed the following:

A slight difference from 5w30 in terms of acceleration, but the engine is quieter on the road.

During hills I noticed an improvement in torque and quietness,

but in terms of fuel economy, I did not notice any change. The same reading for 5w30 oil.

The manufacturer recommends 5w30 to save fuel and recommends 5w40 for protection. Something strange from Hyundai

 

[goingplacesanddoingstuff]

You sure you live on earth? because from my understanding not even death valley has ever reached 136 F.

Saudi Arabia ranges from 50 to 125 F. I would think 5w40 is perfect.

 

[LimeLightLemon]

I would run 5w-40 in your case

 

[Yukiwari]

weird update on X-cess 5w40 i noticed decrease of engine temperature doing highway drive 194F min and 199 high , before with eco lite 5w30 was 199F min goes to 212F what does it mean is high viscosity oil reduce temperature?

 

[Petr]

The reasons might be a combination of oil thermal conductivity, bigger oil thermal capacity, lower friction due to higher HTHS, different air humidity/air pressure or even placebo.

Anyway, it does mean that the engine is more happy with this 5w-40.