Peer Review oil 101

[lemmiewinks289]

Hello,

I have said things regarding engine oil on a lexus forum not too long ago, but am worried that what I said was a misinterpretation on what I have read here and on the oil 101 basics link.

Here is the link to the thread.
http://www.clublexus.com/forums/performance-and-maintenance/443526-10w-40-too-thick.html

Does anyone have anything to add or correct me on? I only ask this because I want to be absolutely certain that I am not spreading mis information. I'm no expert and have only learned what I have read.

Thanks

 

[jdub]

LOL'ed at "You've been on SM too much"

You are pretty much on the mark, but there are valid counter points. At 180K mileage wise, a synthetic is not going to do a whole lot to help wear wise...the motor is on it's down hill leg. It will help a turbo motor IMO due to the heat a syn oil can take, but on a NA with that mileage the only advantage will be an extended drain on a better oil.

Not saying you are wrong, but the counter point is valid.

Concerning the use of a 10W-40, the same thing applies. Any start-up wear is pretty much moot at this point and if the bearings are starting to show wear, use of a 10W-40 is appropriate due to increased bearing clearances.

One thing a PAO or ester based synthetic will do is throughly clean out the engine. That is a double edge sword. You will have more particulates in the oil as engine deposits break down...not a big problem with a good filter. However, if those deposits are what's keeping worn, shrunk seals from leaking...care to guess what can happen?

The OPs decision to continue to run a dino oil on a motor with those kind of miles is valid. What you are saying is valid as well. It boils down in this case to what the owner wants to do because either will work, especially if he does not want to possibly induce a leak.

 

[lemmiewinks289]

LOL'ed at "You've been on SM too much"

You are pretty much on the mark, but there are valid counter points. At 180K mileage wise, a synthetic is not going to do a whole lot to help wear wise...the motor is on it's down hill leg. It will help a turbo motor IMO due to the heat a syn oil can take, but on a NA with that mileage the only advantage will be an extended drain on a better oil.

Not saying you are wrong, but the counter point is valid.

Concerning the use of a 10W-40, the same thing applies. Any start-up wear is pretty much moot at this point and if the bearings are starting to show wear, use of a 10W-40 is appropriate due to increased bearing clearances.

One thing a PAO or ester based synthetic will do is throughly clean out the engine. That is a double edge sword. You will have more particulates in the oil as engine deposits break down...not a big problem with a good filter. However, if those deposits are what's keeping worn, shrunk seals from leaking...care to guess what can happen?

The OPs decision to continue to run a dino oil on a motor with those kind of miles is valid. What you are saying is valid as well. It boils down in this case) what the owner wants to do because either will work, especially if he does not want to possibly induce a leak.

Ah I see. Well I was confused on how he was trying to validate his points. He never really explained, why he said what he said.

He was on the mark about his claim, but his reasoning was very murky. As if, somone just told him the right thing and he is just pulling things out to fit it around his point.

Thanks for clarification. I will cut and paste what is said here so that people won't think that what he says is wrong. Besides. This makes sense.

 

[jdub]

Go ahead...give me credit if you would. (edit: I see you did - Thanks!)

There is one thing you said that is not accurate:
"Since you are a 10w-40 your start up will be the same viscosity as a 10w-30 oil. It only thickens at higher operating temps."

A 40W multigrade will almost always be thicker cold than a 30W multigrade with the same 1st numbers...it's the nature of the base oil + viscosity improvers. Always keep this in mind when you talk cold vs hot viscosity:

An oil never, ever thickens when it gets hot...it always drops in viscosity the hotter it gets.

The misconception comes from the way the oil spec's are presented with the cold # 1st and the hot # 2nd...for example a 10W-40 implies that the oil will thicken from a 10W to a 40W. The SAE is applying a different stand to cold vs hot...you will see cold (40 deg C actually) viscosity ranges go from ~40 cst for a 0W-20 to over 150 cst for a 20W-50. The standard changes for ops temp (100 deg C)...that same 0W-20 will have a hot viscosity of 9 cst...the 20W-50 will drop to 20 cst. It's easy to make this mistake

 

[IJ.]

So the bigger #2 number will thin less with the temp rise?
(learning all the time)

 

[lemmiewinks289]

Go ahead...give me credit if you would. (edit: I see you did - Thanks!)

There is one thing you said that is not accurate:
"Since you are a 10w-40 your start up will be the same viscosity as a 10w-30 oil. It only thickens at higher operating temps."

A 40W multigrade will almost always be thicker cold than a 30W multigrade with the same 1st numbers...it's the nature of the base oil + viscosity improvers. Always keep this in mind when you talk cold vs hot viscosity:

An oil never, ever thickens when it gets hot...it always drops in viscosity the hotter it gets.

The misconception comes from the way the oil spec's are presented with the cold # 1st and the hot # 2nd...for example a 10W-40 implies that the oil will thicken from a 10W to a 40W. The SAE is applying a different stand to cold vs hot...you will see cold (40 deg C actually) viscosity ranges go from ~40 cst for a 0W-20 to over 150 cst for a 20W-50. The standard changes for ops temp (100 deg C)...that same 0W-20 will have a hot viscosity of 9 cst...the 20W-50 will drop to 20 cst. It's easy to make this mistake

Do'h. That first part was just a mistake. I read this, but plainly just forgot in the face of seeing 10w-30 next to 10w-40. Excuses blah blah.

I kept reading about this misconception in the oil 101 and have to conciously keep telling my self that it thins out as temps rise. Its hard to grab a concept that is the opposite of what is deeply ingrained in my mind.

So the bigger #2 number will thin less with the temp rise?
(learning all the time)

Yes, exactly. The bigger #2 just won't thin as much as the smaller one once op temp is reached.

 

[jdub]

Ian - The reason being is viscosity is a lot higher cold for the heavier weight oils.