Why did Toyota recommend a winter and summer oil?

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I have a 1992 Toyota Camry and the manual recommends a 5-30 for winter ops and a 10-30 for summer time. This is well and good until I read the oil info on this site. The basic message is that even a 0-30 oil is thicker than ideal at normal starting temperatures. A 5-30 is slightly thicker and of course a 10-30 even more so. This is all for starting temperatures. I know that once operating temperatures are reached they all warm up to the same viscosity.
Why in the world did Toyota recommend a 10-30 during summer temps if the 5-30 is still thicker than ideal? 0-30 wasn't widely available back then so I know why it isn't listed but why don't they just list the 5-30 as the only recommended oil? Why even list the 10-30, expect of course maybe for emergency ops when you can't find 5-30?
 
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Just use a 5w30 syn or a 0w30 syn all year long or if your are in a very cold area then pour in the 0w30 in the fall oci.
 
Originally Posted By: rooflessVW
Because in 1992 a 10W-30 was more shear stable than a 5W-30.


Booyah.
 
I would think the engineers who wrote the spec would have known all of the tolerances and oil properties. I just can't think why they would add the 10-30 to the specs when I am sure they must have known that 5-30 is better in all conditions.
 
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Originally Posted By: BrianApp
I would think the engineers who wrote the spec would have known all of the tolerances and oil properties. I just can't think why they would add the 10-30 to the specs when I am sure they must have known that 5-30 is better in all conditions.

1992
 
Originally Posted By: rooflessVW
Because in 1992 a 10W-30 was more shear stable than a 5W-30.


There is an answer. For my curiosity can you explain what shear stable does? Does that, whatever it is, apply today? Would that have made 10-30 the preferred oil then, in 1992?
 
Originally Posted By: BrianApp
I have a 1992 Toyota Camry and the manual recommends a 5-30 for winter ops and a 10-30 for summer time. This is well and good until I read the oil info on this site. The basic message is that even a 0-30 oil is thicker than ideal at normal starting temperatures. A 5-30 is slightly thicker and of course a 10-30 even more so. This is all for starting temperatures. I know that once operating temperatures are reached they all warm up to the same viscosity.
Why in the world did Toyota recommend a 10-30 during summer temps if the 5-30 is still thicker than ideal? 0-30 wasn't widely available back then so I know why it isn't listed but why don't they just list the 5-30 as the only recommended oil? Why even list the 10-30, expect of course maybe for emergency ops when you can't find 5-30?
You are presuming what you read is fact. What you read is more unsubstantiated opinion than fact.
 
Originally Posted By: BrianApp
I would think the engineers who wrote the spec would have known all of the tolerances and oil properties. I just can't think why they would add the 10-30 to the specs when I am sure they must have known that 5-30 is better in all conditions.
Tolerances are the allowed deviation from the blueprint specifications. . What makes 5W-30 better in all conditions?There are cars in other parts of the world with the same engines running different viscosity recommendations . The trend to lighter oils are from the EPA Cafe standards a.
 
From what I have read here ALL oil is thicker that the operating spec, at start, and the lowest first number you can get the closer you get to the designed operating conditions and oil lubrication properties. I never thought about the thickness of oil at start to be much of an issue until I read it here. "%90 of engine wear occurs during the start/warm up."
 
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Originally Posted By: BrianApp
From what I have read here ALL oil is thicker that the operating spec and the lowest first number you can get the closer you get to the designed operating conditions and oil lubrication properties. I never thought about the thicknes of oil at start to be much of an issue until I read it here. "%90 of engine wear occurs during the start/warm up."
All you need to worry about is that the oil will be able to be drawn from the sump to the oil pump. Cold start wear is a factor of many things. Condensation, richer fuel mixture because the engine is cold and the pistons are oval when cold allowing more blow by wash on the cylinder walls. The clearances are more because the parts aren't expanded, Looser parts means more wear. The heat activated additives in the oil aren't activated .
 
Is there an advantage to 10 vs 5 in the summer?
when I get oil next week the 5 is right next to the 10. For those in the know, which is better with today's oil technology?
 
Originally Posted By: BrianApp
Originally Posted By: rooflessVW
Because in 1992 a 10W-30 was more shear stable than a 5W-30.


There is an answer. For my curiosity can you explain what shear stable does? Does that, whatever it is, apply today? Would that have made 10-30 the preferred oil then, in 1992?


Yes, that is exactly what he said. Things like this were different then or around the time you were born.

Spend some time searching and reading the older threads here and you will move up the learning curve pretty quickly.
 
My Aunt bought a brand new 1990 Camry and those 2.0L were bulletproof to start with. She ran PYB 10W30 year round. Sold the car in the early 2000s with over 250 thousand miles on it & still running good with the 5spd. I would run 5W30 now & not blink an eye.
 
Originally Posted By: BrianApp
Is there an advantage to 10 vs 5 in the summer?
when I get oil next week the 5 is right next to the 10. For those in the know, which is better with today's oil technology?
Probably not enough to make a difference.
 
I posted in your ToyotaNation thread.

5w30 wasn't so shear stable, and they were a frightened bunch of people back then, afraid to try new things.

Use 5w30 or 0w30 year round with confidence.

I have a bunch of Mobil 1 0w30 that I bought on clearance sitting in my garage waiting to go into my Camry.
 
1990 conventional oils 10w30 having less Viscosity Index Improver, than a 5w30, so the 10w30 wouldn't become at operating temperature, just a 20 after a few thousand of miles, or way later. They feared a less than SAE30 oil, like 20 weight, haha.
grin.gif
 
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Pretty sure my 2002 camry "allows" 10w30 in summer. Is there a hard upper temp limit for 1992's 5w30?
 
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