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Old 10-19-2012, 08:59 PM   #1
Charlton
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2002 Forester S
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Default 10W30 High Mileage Forester

So i decided to run 10W30 in my Forester with 155K miles.

I figured the heavier weight would offer more protection. I live in Tennessee US where the coldest it gets is 20 degrees F.

Is this ok?
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Old 10-19-2012, 10:53 PM   #2
subaru-tech
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id continue to run 5w30 in it.My 99 impreza has 230k on it and still gets 5w30
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Old 10-23-2012, 04:18 PM   #3
Vince F
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the first # is the weight of the Base oil with heat activated thickeners to make it a 30 weight multi. I run 5W30 in the winter, and 10W30 in the summer. The thickeners are said not to be lubricants, so the fewer the better, especially in the summer.
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Old 10-23-2012, 06:42 PM   #4
chazly413
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The first number is also the weight of the oil when the oil is cold. So, your weight at operating temp isn't very, if at all, different.
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Old 10-23-2012, 07:20 PM   #5
Tmibiker
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I've got a '02 NA Impreza with 115k on it, and I'm running M1 High Milage10W30 in the summer, and I plan on changing it to Mobil 1 High Milage 5W30 for the cold Michigan winter.

Dunno if that's crazy or not.
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Old 10-23-2012, 11:31 PM   #6
Vince F
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Quote:
Originally Posted by chazly413 View Post
The first number is also the weight of the oil when the oil is cold. So, your weight at operating temp isn't very, if at all, different.

Then why is it called Multiviscosity, and why 2 #'s, like 5 & 30, or 10 & 30?
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Old 10-24-2012, 01:22 AM   #7
chazly413
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The first number represents cold viscosity and the second number represents warm viscosity. There is no reason to not run the lowest cold viscosity you possibly can, given that all oil is always too thick when the engine is cold. The problems you start to encounter with going for the thinnest cold viscosity possible, however, is mainly money (something like a 0w-50 is not cheap) and the additive package is going to wear out as the oil ages which will reduce the viscosity difference (not ideal).

Oils start out as either the cold or the warm viscosity when being produced (I can't remember which one is which for synthetic and dino but I know they're the opposite of each other) and then an additive package is added so the oil can effectively be a different viscosity at a different temperature.

NOTE:
Oils are much, much, much more confusing than one would think. I have probably messed something up in my explanation, it's late, feel free to correct or elaborate.
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Old 10-24-2012, 06:44 PM   #8
bluesubie
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Quote:
Originally Posted by Charlton
So i decided to run 10W30 in my Forester with 155K miles.

I figured the heavier weight would offer more protection. I live in Tennessee US where the coldest it gets is 20 degrees F.

Is this ok?
I prefer to go with High Mileage oils. HM oils within the same grade will have a thicker viscosity, higher High Temp High Shear, more seal conditioners, and more anti-wear additives than a non-HM oil. I've had good luck with MaxLife synthetic blend and Pennzoil High Mileage Conventional, both in 5W-30, in a 99 Outback and 00 RS.

A 5W-30 and a 10W-30 are both a 30 weight at operating temp, BUT a 10W-30 will generally have less viscosity improvers which are the first thing in oil to break down.

Your owner's manual states that you can use 10W-30 and 10W-40 down to -4F. A 5W is actually tested at -30C and a 10W is tested at -25C.

http://www.pqiamerica.com/coldcrank.htm

-Dennis
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