Higher viscosity in summer heat??

[Sonic]

I see alot of people post that they run a higher viscosity oil in the sumer months. Like 5w20 in winter then 5w30 or 10w30 in summer. I understand that the higher weight oil can provide better protection but isn't that because it is a bit thicker (more viscous) at operating temps? I guess what I'm asking is if a 5w20 might run a motor a smidge cooler compared to a 5w30? Or do I have this backwards? Seems like the less resistance the motor has on it the cooler it'd run. Wouldn't a more viscous oil be harder to cool down too? And shouldn't a motor run about the same temp in cold and hot weather with the same weight oil?

When I used to go to the oil change shop they would always tell me I wanted 5w30 in summer for my van that is spec'd for 5w20. So I'd run the 5w30 and switch back to 5w20 when it started getting cold. I just started changing my own oil agian last summer and did use 5w30 but then went to 0w20 in november for the cold weather. Also, would a Xw20 get to operating temps quicker than a Xw30?

If you guys can clear up my confusion I would greatly appreciate it!

 

[jstutz]

I think it is mostly just a trade off of cold weather viscosity. When the weather is warm, any xw30 flows plenty good at startup but you get the "better" high temp performance. During cold winters, the thought is that you want the much better cold weather flow at a very slight degradation of high temp performance. In reality the small differences probably dont matter but i believe this is the thought.

 

[Chris142]

An engine needs to run between 180F and 230F to operate properly. If it gets much hotter than 230F engine damage will occur. Your engine does not run that much hotter in summer than in winter. There is no reason to run a thicker oil in summer.

 

[NateDN10]

Oil viscosity has no effect on how hot the engine runs.

Some, however, choose to run a lower viscosity oil in the winter if they anticipate doing a lot of relatively short trips where the oil will never get up to rated temperature.

If your van is specced for 5W-20, it's safe to use it year-round. Change based on mileage, not based on season.

 

[glum]

One thing I never see mentioned in these (endless) discussions is overheating. If your engine overheats and you manage to shut it down before something catastrophic occurs, aren't you better off with thicker oil, as far as heat-related wear?

 

[mechtech2]

Lots of good advice above, EXCEPT for the comment that oil viscosity has no effect on how hot the engine runs.

Heavy oils can for sure cause hotter running temps.
My empirical and vicarious experiences show thicker oils have more drag and cling, and can cause hotter oil!
Something like temps 10 deg F cooler on the highway with 10-40 vs.20-50.
It would be a miracle for hotter oil to make an engine stay the same overall temp as with cooler oil.
[coolant temperature is greatly irrelevant here]

A slightly thicker oil in summer can be anywhere from OK to smart.
Oil runs hotter and thinner.
The thicker oil in summer can be THINNER than thin oil in cool weather!

 

[Tempest]

The thermostat in your car determines how hot your engine runs. Any thermostat will have a setting higher than any ambient condition.

Running a thicker oil in hot weather, so long as your cooling system is adequate and working properly, will get you nothing.

 

[OVERKILL]

Originally Posted By: Tempest
The thermostat in your car determines how hot your engine runs. Any thermostat will have a setting higher than any ambient condition.

Running a thicker oil in hot weather, so long as your cooling system is adequate and working properly, will get you nothing.


Oil temp and coolant temp are not the same.

 

[MonumentOiler]

Originally Posted By: glum
One thing I never see mentioned in these (endless) discussions is overheating. If your engine overheats and you manage to shut it down before something catastrophic occurs, aren't you better off with thicker oil, as far as heat-related wear?


If you are worried about overheating then I would focus on preventing that rather than using thicker lube. I don't think overheating is a common problem with good maintenance.

Once the temps are above the range the weights are calculated at then performance is not guaranteed. A quality synthetic 5w-20 might maintain viscosity and lubrication better than a cheap 10w-30. Testing at that temp would probably be needed to know what "overheated" performance was like.

 

[ahoier]

All comes down from the "old timers" who thought "thicker is better" - but in today's modernized engines, that's really no longer the case. You really want to go with what the manufacturer calls for; deviate (err...."meet in the middle" per se...) somewhere between what's spec'd on the "oil filler cap" and the viscosities listed in the owner's manual.


My 07 and 08 Kia's both spec'd 5W-20 on the filler cap; but the OWNERS MANUAL stated that depending on the "ambient temperature" 10W-30 or 5W-30 would also be "compatible"....

 

[Tempest]

Originally Posted By: OVERK1LL

Oil temp and coolant temp are not the same.

Car companies test their cars in extreme heat, to include Death Valley in summer time, with factory stock (obviously) cooling systems.

If the manual recommends going up a grade at a particular temp, then do it. Otherwise, I see no need. I've lived in a dessert for 20 years using just stock oil grades without issue.

If one has heavily modified their car or racing it, then the manual goes out the window.

 

[OVERKILL]

Originally Posted By: Tempest
Originally Posted By: OVERK1LL

Oil temp and coolant temp are not the same.

Car companies test their cars in extreme heat, to include Death Valley in summer time, with factory stock (obviously) cooling systems.

If the manual recommends going up a grade at a particular temp, then do it. Otherwise, I see no need. I've lived in a dessert for 20 years using just stock oil grades without issue.

If one has heavily modified their car or racing it, then the manual goes out the window.


Precisely. Now think of this the other way.

Since oil and coolant temps are not 1:1, it would be fair to assume that in the frigid cold winter, oil temperatures may get nowhere near what they would reach in the summer. Even with the coolant the same temperature.

In cases like this, it may be beneficial, if conditions (both mechanical and ambient) allow the move to a lighter oil to improve start-up performance and to get closer to your summer "hot" viscosity, which is likely closer to "optimal" for your engine.

 

[qdeezie]

I'm a die hard 5w-30 guy, but if I find a SWEET deal on 10w-30 oil, I will purchase it and use it during the spring/summer months only because I know I don't need the extreme cold startup protection that 5w-30 offers during the summer months and I have the same viscosity at the normal operating temperature. I don't buy heavier viscosity oils for any other reason than this.

 

[Sonic]

Heavy oils can for sure cause hotter running temps.
My empirical and vicarious experiences show thicker oils have more drag and cling, and can cause hotter oil!
Something like temps 10 deg F cooler on the highway with 10-40 vs.20-50.

This is why I get confused. If a thicker oil can result in higher oil temps, why use it in summer? It seems like there is a line that can be crossed where either you get better protection but higher oil temps or you can get thinner oil that may run cooler but maybe less protection? But how do you know where that line is? Like my v-twin motorcycle can use 10w40 or 20w50. I use the 20w-50 because everyone tells me it needs the protection of that 50 weight oil being air cooled. But would it run cooler with 10w-40 making the 40 weight an adequate viscosity for protection? Almost seems like the higher viscosity oil has to protect itself from itself! If it runs hotter, it needs more protection.

While cruising down the highway at 70mph in my van, shouldn't the oil temp be the same regardless of the outdoor temp?
I think I'll just keep on with the 5w20 through the summer with my van. It is a short tripper most of the time anyway.

 

[Sonic]

Originally Posted By: qdeezie
I'm a die hard 5w-30 guy, but if I find a SWEET deal on 10w-30 oil, I will purchase it and use it during the spring/summer months only because I know I don't need the extreme cold startup protection that 5w-30 offers during the summer months and I have the same viscosity at the normal operating temperature. I don't buy heavier viscosity oils for any other reason than this.


I understand that. Running a 10w over a 5w in summer is fine. Over the winter I ran 0w. It's just the operating temp viscosity that get me thinkin'.

 

[CATERHAM]

The bottom line is actually oil pressure, or to be more specific oil back pressure.
Run the lightest oil that provides the minimum OP as spec'd by the mftr. In the summer the oil temp's may get hotter under certain conditions resulting in lower OP which may require the use of a slightly heavier oil.
In the winter oil temp's may not reach the optimum minimum of 180F resulting in higher oil pressure meaning a lighter oil can be used which has the added benefit of improved cold starting.
It really is that simple.

 

[sangyup81]

It's more that you can get away with using a thicker oil in the Summer. I don't think there is any need but I have done it before due to specials on thicker oils.

 

[Tempest]

Originally Posted By: OVERK1LL

Precisely. Now think of this the other way.

Since oil and coolant temps are not 1:1, it would be fair to assume that in the frigid cold winter, oil temperatures may get nowhere near what they would reach in the summer. Even with the coolant the same temperature.

In cases like this, it may be beneficial, if conditions (both mechanical and ambient) allow the move to a lighter oil to improve start-up performance and to get closer to your summer "hot" viscosity, which is likely closer to "optimal" for your engine.

His question was about high heat, not extreme cold. If you live in areas that get deep into the negative F, then I agree that a lower grade maybe beneficial. This is because oil viscosity change is not linear. There is a much greater change at lower temps than there is at higher temps.

 

[Tempest]

Originally Posted By: CATERHAM
The bottom line is actually oil pressure, or to be more specific oil back pressure.
Run the lightest oil that provides the minimum OP as spec'd by the mftr. In the summer the oil temp's may get hotter under certain conditions resulting in lower OP which may require the use of a slightly heavier oil.
In the winter oil temp's may not reach the optimum minimum of 180F resulting in higher oil pressure meaning a lighter oil can be used which has the added benefit of improved cold starting.
It really is that simple.

Only problem with this is finding the spec. and that a lot of cars don't come with OP gauges.

 

[oldmaninsc]

Originally Posted By: Tempest

Only problem with this is finding the spec. and that a lot of cars don't come with OP gauges.

Agreed, plus on my 3 vehicles that have oil pressure gauges, the gauges are nothing more than a glorified idiot light.
On both Fords after starting the engine, the gauge goes about half way and stays there regardless of operating temp., RPM, etc.
On the Trailblazer the gauge would move from 40 - 60 psi when the RPM rose (as would be expected for obvious reasons) but we found out from an engineer that the PCM "told" the gauge what to read - it wasn't the actual PSI.