0W-40 engine oil

[supramkivtt2jz]

Originally Posted by bluesubie

So, um. OK. You're welcome.
You said that the 40 grade is thicker but at operating tempurature the difference is "negligible ". My point is just that it's not negligible.

-Dennis

I understand what youre saying, but If i lived in a hotter environment, i would probably explore the idea of a higher weight oil. I dont utilize a particular weight for any specific application of my vehicle. Bob's initial chapters state that nearly all weights reduce to essentially the same kinematic viscosity at 100 *C. Since the engine operates at such a large range at oil viscosities (as the oil warms), i dont see a problem in using something that is just a few cST's higher at operating temperature - especially when damage is done at startup anyway.

Originally Posted by Admiral Ballsy

You're handwaving away the pretty significant difference in chemistry. A 40-point viscosity spread is pretty extreme and requires a LOT of friction modifier - but you'd know that, right? Since you read Bob.

Im expecting you to clarify your statement.

Originally Posted by sierra

So I read chapter 8 and it says.

There is one more thing. A 20 grade oil is not half as thick as a 40 grade oil. The real scale is more like the oils having an absolute thickness of 108 and 114. Now it can be seen that the 40 grade oil is only around 10 percent thicker than the 20 grade oil. The difference is not that much at operation but at startup the difference is significant. Pressure / flow dynamics go along with this 10 percent figure. A 30 grade oil should be thought of as having an absolute viscosity of 110 and a 50 grade oil has an absolute viscosity of 120. I am talking about the viscosity at operating temperatures.

However I find that confusing because when I compared a 0w-20 oil with a 0w-50 oil the viscosity at operating temp 100c was 6.7 and 18.7 respectively. Surely that makes the 0w-50 almost 3 times as viscous at 100c than the 0w-20 oil?

My understanding is that the SAE viscosity range is the kinematic viscosity whereas bob's statement is relating to absolute viscosity. Absolute accounts for flow dynamics and friction - something i know nothing about.

[Admiral Ballsy]

Originally Posted by Rayme

What you're saying is that a 0w40 oil has less lubricating properties than a plain 40w Right? Because of the added friction modifiers there is actually LESS lubrification content.

DOH. I meant VI modifiers, not friction. I changed differential lube in my truck yesterday, had that on my mind.

I don't know about lubrication properties, but IMO - and the O of a fair amount of folks on the bobsite, the amount of VIIs you gotta use to get a 40-point spread is too extreme. It appears that 0W40 doesn't have a very good reputation for long-term stability.

[bluesubie]

Originally Posted by sierra

However I find that confusing because when I compared a 0w-20 oil with a 0w-50 oil the viscosity at operating temp 100c was 6.7 and 18.7 respectively. Surely that makes the 0w-50 almost 3 times as viscous at 100c than the 0w-20 oil?

Exactly!

Originally Posted by Admiral Ballsy

I don't know about lubrication properties, but IMO - and the O of a fair amount of folks on the bobsite, the amount of VIIs you gotta use to get a 40-point spread is too extreme. It appears that 0W40 doesn't have a very good reputation for long-term stability.

In the old days (only a few years ago in the lubrication world) oils with a large viscosity spread were very unstable. As base oils and viscosity modifiers improved, 0W-40's are more stable today than they were even two years ago. Mobil1 0W-40 is a good example. It was known to always shear to a 30 grade in many applications, but the new API SN formula has been known to stay in grade very well in used oil analysis. It did well at 5k+ mile intervals in my Forester turbo which is an oil destroyer and Subaru recommends 3,750 miles for my model year regardless of the oil or driving conditions.

There are still some advantages though to the narrower spread. Even though viscosity modifiers have improved, they are still used for a wider spead in typical oils and the narrower spread oils are sometimes less volatile and more stable. If you compare oils that list their NOACK volatility (like Amsoil) a 5W-20 is usually less volatile than a 0W-20 which may mean less evaporation of the oil.

For the record, the article linked above at bitog was not written by the original owner of Bob's, someone in the lubrication industry, or even an engineer. It was written by a doctor in Florida. I don't have industry experience either, but I did stay at a Holiday Inn Express last night.

While there is some good information in the oil 101 article, some of it is very confusing. If you want a slightly clearer picture of actual viscosity at a given tempurature try using a viscosity chart/graph. http://www.widman.biz/English/Calculators/Graph.html
The chart isn't as accurate once you go below 0C according to the web site owner.

There are a few very bright people in the industry, as well as some engineers and chemists that post at bitog, although you really have to sift through a lot of "noise" to get to the right info. And post count definitely does not represent industry training or knowledge.

I love oil threads because they usually cover 5 or 6 different topics. Oh, and for the record -

-Dennis

[No Limit Motorsport]

Originally Posted by bluesubie

Exactly!

-Dennis

You sound like you know a lot of oil.

Do you mind if I ask whether you work in the industry? Went to school for chemical engineering? Or just a well informed enthusiast?

[bluesubie]

Originally Posted by No Limit Motorsport

You sound like you know a lot of oil.

Do you mind if I ask whether you work in the industry? Went to school for chemical engineering? Or just a well informed enthusiast?

No, see my note above. I'm just an enthusiast, that followed bitog closely in the earlier days when more tribologists and very knowledgable engineers posted there. I've also been corrected many times by people in the industry and I'm sure I'll be corrected if my above info is off base.

-Dennis

[Jertronic]

do you guys trust the toyota 0W-20 syn? That's what i had put in yesterday for my oil change. I don't track my car so i figured it was fine......

used to use Motul in my BMW 328

[bluesubie]

Originally Posted by Jertronic

do you guys trust the toyota 0W-20 syn? That's what i had put in yesterday for my oil change. I don't track my car so i figured it was fine......

used to use Motul in my BMW 328

It's highly regarded at bitog for having a high Viscosity Index and being one of the lightest 0W-20's at start-up. High visocosity index usually means less change in viscosity (thickening or thinning) over the oil change interval. Whether or not that makes it a good oil for the FR-S/BRZ I don't know, but it's probably fine.

There have been some uoa's here on the Idemitsu/Subaru 0W-20 and they've been good. The Toyota oil is made by Exxon Mobil, but it is a different formulation than Mobil1 0W-20. Motul has a good 0W-20 as well.

-Dennis

[sierra]

I would also add, to the comments that higher grades have neglible viscosity differences at operating temperatures, my experience.
When I changed from the 0w-20 to 5w-40 my fuel consumption increased quite dramatically. Even when I changed it again within a week to 5w-30 the difference was obvious and i'm looking forward to getting back to the original consumption next month when it gets 0w-20 at the first service.