[quote=chamberlain;11275704]My initial concern with 5W-40 was the shearing of the additive package.

If I understand it correctly, you start with a base weight oil, and add viscosity enhancers that bring it up to a 40 weight oil when it's hot. So 15W-40 is a 15 weight base oil with enough viscosity enhancers to bring it up to 40 weight when hot. 5W-50 is a 5 weight base oil with more viscosity enhancers, and 0W-40 is a 0 weight oil with yet even more viscosity enhancers.

Now, we hear that the High Pressure Oil Pump in the 6.0L is hard on the oil and shears out the additive package. Exactly how much over 5000 miles I don't know. I don't think I've seen it quantified. But, let's say for the sake of discussion that in 5000 miles the engine shears out 50% of the additives. Of course there is more to the additives than just viscosity enhancers, but for the sake of this post they are what we are concerned with.

Using our theoretical 50% and assuming the additive effect is linear, 25 of the 40 weight in 15W-40 is additive (40-15=25). If half of the additive shears out (25/2=12.5) then you are left with 15W-27.5 at the end of the 5000 miles. 27.5 being the base 15 plus the remaining 12.5 of additive.

35 of the 40W in 5W-40 oil is additive, so after 5000 miles you are left with 5W-22.5 (35/2=17.5+5=22.5).

And, 40 of the 0W-40 is additive, so after 5000 miles you are left with 0W-20.

Now, this could all be speculative BS for all I know. The only way to really know would be to take all of the different weights and types of oil, run them in a test engine for an equivalent of 5000 miles and do an oil analysis on them. I've seen a number of oil analysis, but I've never seen viscosity of used oil in terms of "weight". Usually some other number that measures viscosity.[/quot


Send your oil sample to a analysis Co. like Blackstones and they will inform you what viscosity still remains. When I used 15w-40 my report would come back as still a 40 weight, but when using 5W-40 it will come back reading 30 weight.

 

Blackstone lists two viscosity numbers. "SUS Viscosity @ 210F" and "cST Viscosity @ 100C". I've never tried to figure out what those numbers represented and how they related to weight, but it appears that there are some tables online that come close.

 

http://www.engineeringtoolbox.com/vi...ter-d_413.html

Kinematic viscosity can be converted from SSU (or SUS) to Centistokes (cSt)"

νCentistokes = 0.226 νSSU - 195 / νSSU

where

νSSU < 100

νCentistokes = 0.220 νSSU - 135 / νSSU

where

νSSU > 100

 

Also:
SAE 5 weight viscosity range - 3.8 to 4.09 cStokes
SAE 10 weight viscosity range - 4.10 to 5.59 cStokes
SAE 15 weight viscosity range - 5.6 to yyy cStokes
SAE 20 weight viscosity range - 5.6 to 9.29 cStokes
SAE 30 weight viscosity range - 9.3 to 12.49 cStokes
SAE 40 weight visciosity range - 12.5 to 16.29 cStokes
SAE 50 weight visciosity range - 16.3 to 21.8. cStokes
SAE 60 weight visciosity range - 21.9 to 26.1 cStokes

hgere is a good discussion on the subject:
http://www.zddplus.com/TechBrief13%2...0Viscosity.pdf

 

Cheers to David for hitting the nail on the head.

 

In layman terms:

SUS is just measurement derived from a type of viscometer measuring the time it takes 60ml (factored up or down at will) of whatever fluid at 210F in this case to flow though a hole and is pretty outdated and very temperamental.


ST is based on Stokes Law and in layman's terms is based on the drag of a calibrated sphere falling through a liquid (210F oil in this case and assuming Blackstone is using this method) and measuring the time it takes to pass through two set points. A bunch of alg/calculus later you come to a Stoke. For example: room temp water should be around 100 Stokes IIRC. The "c" in cST is just a Stoke/100 =cST. If the above method is being used to find cST it's a much better test for our trucks because of the drag factor which in the same realm as shear. But ST/cST is just a unit of measure and can be derived from any number of viscometers but it sounds like Blackstone is still using SUS so they're using the old school method and calculating cSt from that but they may have other viscometers.. Who knows.

Now these only work with Newtonian fluids such as our mineral oil based engine oils. Hope that makes sense, I could probably spell it out over the phone a lot better.

 

Some oils can achieve a multigrade rating without VI's (polymers) - typically these are the PAO type synthetics.

A multigrade rating is just the SAE viscosity at two reference temps. Low number is not always at a specified temp, but represents a relative "flowability" (not a specific viscosity reference like the higher number) in winter temps - commonly around 0*C IIRC. The high number is a SAE viscosity reference at 100*C.

So - the bottom number is NOT the weight (or viscosity reating) of the base oil. Other than that, the concept of formulating a multi-grade oil is as discussed. The W stands for winter (not weight).

 

I retired several years ago, but on occasion I do R&D work for a company that supplies the military and homeland security of this country and others with a device that does non intrusive inspection. It can be put up against a drum of gas and it will determine whether it is high test or low test, or it can determine whether a diesel fuel is taxed or not. The primary reason it was designed for is to look for explosives and or to verify the contents match the manifest, but I see no reason why this type of device couldn't determine any viscosity of any liquid at a given temp. It works on sound along with heat and another reading I am not familiar with. About the size of a police radar gun, and 1/2 the price of a Lariat Super Duty.

 

oh wow good price. Can you get your hands on one for some testing purposes?

 

Next Wed. a engineer/representative from the company will be meeting me to buy off on some inspection fixtures I built for them. I will definitely ask him about this viscosity subject.

 

[QUOTE=ljutic ss;11275980]I agree with dchamberlain, and ljutic.... I have been sending oil samples to Blackstone labs for years, everything from high performance stroker japanese motorcycle engines to 12 and 16 cylinder GE and EMD (General Motors) locomotive engines, and everything in between, and NOTHING I have sampled shears the oil quite like a 6.0.

In the early days of my 6.0 ownership (the one I bought new is a May '03 build), I thought something was wrong with my 6.0 due to the oil sample reports. Many of the 6.0's I have sampled have shown fuel dilution along with the shear, but many will reflect the shear with little or no fuel dilution. They definitely return reports that look quite different than any other similar (in design) V-8 diesel. I have always changed at 3k, which helps, and I have run Delo since the the second change at 6k.

Anyway, blah, blah, blah... everyone have a good night.

 

How did you figure out you needed to change just #8?

 

When I bought my truck a couple of months ago I had the dealership change all filters and fluids, but from what I'm reading everyone recommends 5w-40 syn. Is one brand better than the other, Rotella vs Mobil (class III or VI)?

It's too soon for an oil change but 5w-40 will allow me to put in Rev-X and may help with some of my issues on power loss and warm up time.

 

I heard Rev-X will also help with your seat warmers and will increase your top speed, one guy even reported getting "100 more torques" from Rev-X.

 

I tried valvaline blue and that's when I started feeling studdering. I changed back to rotella and rev x and it was gone