Why do people run higher weight oil in summer?

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Like Brian553 said above, oil temperatures are slightly higher in the summer. Why? Because there is heat transfer from the sump to the air outside, very simply. Also, cold air getting to the metal parts under the hood also transfer heat out. On some engines, not many, the ones that have an oil-to-water heat transfer device, it is a little bit better controlled though.

One shouldn't feel like that have to use 5w30 in summer and 0w20 in winter (for a car spec'ed to 0w20 or 5w20) but you could for a small amount of extra wear protection. Not much.
 
Originally Posted by hallstevenson
Originally Posted by Onetor
Some Owner's Manuals require a thicker viscosity at higher ambient temperatures. Check your OM. Just look at the viscosity our friends in Australia use....
How many modern vehicles say to do that ? Honestly asking. In the 60s, yeah, but today ?


The 2019 Subaru WRX manual indicates:

Engine oil viscosity (thickness) affects fuel economy. Oils of lower viscosity provide better fuel economy. However, in hot weather, oil of higher viscosity is required to properly lubricate the engine.

My 2006 Saab 9-2x, which is a rebadged WRX, has the following statement:

If the vehicle is used in desert areas, in areas with very high temperatures, or used for heavy-duty applications such as towing a trailer, use of oil with the following grade and viscosities is recommended.

API classification SL (or SJ): SAE viscosity no.: 30, 40, 10W-50, 20W-40, 20W-50
 
Here's a couple direct quotes from a Mazda3 owner's manual. Read between the lines and it says, 0w-20 gives better fuel economy and 5w-20 or 5w-30 lubricate the engine better. FWIW, I use the USA recommended viscosity year round.

US_Oil.JPG


Mexico_Oil.JPG
 
Originally Posted by circuitsmith
Originally Posted by ARB1977
Run what the manufacturer recommends and be done.

And yet you use unapproved Amsoil in your Toyota.

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Yes, you will often run a hotter temp in the summertime. How about a 100 deg day where you have the AC on and are stuck in slow moving traffic for a half hour? I'd rather have the extra margin of safety with the higher viscosity, especially if it's allowed in your vehicle anywhere in the world. What if your cooling system isn't operating at 100%? I'd bet few of them do for 5-10 yr old vehicles with original components. Again, I'd prefer the higher margin of safety with the next viscosity grade up (ie 20 to 30 grade).
 
Originally Posted by circuitsmith
Originally Posted by ARB1977
Run what the manufacturer recommends and be done.

And yet you use unapproved Amsoil in your Toyota.


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Because they are right and engineer is just a pencil pusher that is trying to meet Cafe' standards so he can get his bonuses.
 
Originally Posted by Whammo
I have seen a lot of people recommend running a 5w30 instead of a 5w20 in summertime. As far as I know, the engine operating temp isn't going to be higher in the summer. If the manual says 5w20 is fine year round, why mess with it?

The manual is about fuel economy numbers mandated by the EPA/nonsense.

As far as you know, is wrong. The engine operating temp is higher in summer. Realize that there is a delayed reaction. The thermostat is set for a temp, but the cylinder temp is higher when the ambient is.

The radiator fan is set for a temp, but again it is a delayed reaction. It matters less today with modern oils, especially synthetic, but ultimately there is no magic here.

The base oil weight is what dictates steady state operation. The -V weight just dictates the cold flow. The second number is what you pick for the operational environment at normal ambient and running temp.

Ignore this if you wish.
 
Originally Posted by Dave9
Originally Posted by Whammo
I have seen a lot of people recommend running a 5w30 instead of a 5w20 in summertime. As far as I know, the engine operating temp isn't going to be higher in the summer. If the manual says 5w20 is fine year round, why mess with it?

The manual is about fuel economy numbers mandated by the EPA/nonsense.

As far as you know, is wrong. The engine operating temp is higher in summer. Realize that there is a delayed reaction. The thermostat is set for a temp, but the cylinder temp is higher when the ambient is.

The radiator fan is set for a temp, but again it is a delayed reaction. It matters less today with modern oils, especially synthetic, but ultimately there is no magic here.

The base oil weight is what dictates steady state operation. The -V weight just dictates the cold flow. The second number is what you pick for the operational environment at normal ambient and running temp.

Ignore this if you wish.



It's not about ignoring anything. The OEM states what grade to use. I have used other than the recommended grade because I know using a 30 grade where a 20 grade is recommended because extra human hair thickness won't hurt anything. All you stated is 20 grade recommendation is for better fuel economy which is true but there is no evidence using a 30 grade provides longer engine life over a 20 grade.
 
Originally Posted by Whammo
As far as I know, the engine operating temp isn't going to be higher in the summer.


Well, that depends.

When I am pulling a heavy trailer in the winter, it is easy to keep all the temps "normal".

But in the summer - esp with the AC on - everything is up near the very maximum edges of "normal".
 
Originally Posted by DoubleNickels
Because they know better than the engineers who designed the motor and specified the fluid.


Hmmm, is it possible the engineers spent a lot of time and money coming up with those oil recommendations? I say yes... and that oil recommendation is the "sweet spot" so to speak, suitable for probably 99.99% of the applications. Maybe it's happened to some guy, somewhere in Timbuktu but I personally have never heard of someone ruining their engine by running the OE spec oil. Deviate from it at your own peril..
 
Thicker oil protects better especially in summer heat. If you like 30 in summer, use it in winter as well. If you prefer 0 (as oppose to 5) for winter, use 0Wx30. It may be pricier.

Those in the know, will never use thin oil
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Originally Posted by maxdustington
Old habits from when oils were trash. Back in the days when you ran SAEx in the summer and 10W30 in the winter.

Lack of cold starts means you can get away with a 15Wx if you want. You can run cool fleet oils in the summer like DELO 400 SD 15W30.

Thicker oils like 10W30 seem to be disappearing from store shelves. I'll bet there are a few members who have a ton of 10W30 they got cheap that plan to run it in the summer to be safe.

BITOG tradition to ignore manual recommendations!





Indeed I got 5 to 6 jugs of Pennzoil 10w30 that i got for 5 dollars a jug when they clearanced it out at walmart and will only run it in the summer


also got some Delo that was on clearance at a different time

and then some Mystik 10w30 that was clearanced at Fleet Farm.


I mainly got 10w30 in some cases only because all weights were on clearance but the 5w30 disappears the quickest and I'm sometimes late to the party so I just take what I can get.
 
Originally Posted by Black_Thunder
10w30 that i .... will only run it in the summer.
I mainly got 10w30 in some cases only because all weights were on clearance.......... so I just take what I can get.



If it makes you feel better, mix it 50/50 with some good 0W-20 and call it a day
 
Whammo said:
I have seen a lot of people recommend running a 5w30 instead of a 5w20 in summertime. As far as I know, the engine operating temp isn't going to be higher in the summer. If the manual says 5w20 is fine year round, why mess with it?[/quote]

That's a fantastic question..My guess is some people have a solution that's in need of a problem.

Unless there's some compelling, objective reason to switch to the higher weight, stick with what's working for you.
 
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Originally Posted by circuitsmith
Originally Posted by ARB1977
Run what the manufacturer recommends and be done.

And yet you use unapproved Amsoil in your Toyota.

Haters gonna hate...sounds like someone can't afford Amsoil. Running their XL line. I run 5W30 what the manufacturer calls for and 0W20 what Honda calls for. I don't care if their not API certified.
 
Originally Posted by Whammo
I have seen a lot of people recommend running a 5w30 instead of a 5w20 in summertime. As far as I know, the engine operating temp isn't going to be higher in the summer. If the manual says 5w20 is fine year round, why mess with it?


Actually its quite sane to use a higher weight oil operating your vehicle in hot weather. Of course the oil operating temperature is going to be higher in the summer. In some cases depending on vehicle and use much higher. Oil temperatures are not controlled by a radiator and thermostat like the coolant is except in cases of some vehicles outfitted for heavy duty towing.

Its silly to think that oils temperatures will be the same in my state where temps have been a constant 90 to 100 degrees for weeks now compared to cooler areas of the country. In fact, since I no longer live in a colder state, its silly for me to use anything but a 5w30 year round. I do not need a 5w20 like someone upstate NY with wintertime temps in the 0 to 40 degree range.

The manufacturer recommendation of 5w20 is a blanket recommendation, average if you will, for the entire continent, you can fine tune that to your climate. 5w20 oil is of no use to me when I start my truck up in 90 degree heat. In fact a straight 30 would be fine.
Furthermore the 5w20 its for fleet fuel mileage in mind, for the best EPA results they can get.

If you stick with your manual you will be fine but there is a good reason to fine tune your weight oil to your area, most people are not capable of this but its not rocket science.
If makes FAR MORE sense to fine tune your weight oil then select one brand over another brand if they meet the same API. Now that is something that makes no sense, choosing one oil brand over the other when they meet the same API. Conventional and synthetic ... :eek:)
 
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