No Rotella T6

[ruffdog]

Well, after reading a bunch on the subject of oil viscosity, I found out there is another number that is more important than just the weight of the oil.

"High Temperature High Shear HTHS viscosity measures the viscosity of an engine lubricant at 150°C and simulates the narrow tolerances and high speeds between moving parts in a hot engine. In particular bearings, the camshaft, the piston rings and liner."

So, normally, a 15w40 oil will have a higher HTHS number (~3.7) than the lower weights. Basically, the higher the number, the more heavy duty the oil is. You can get lower viscosity oil with a good HTHS but you pay for it.

Lately, the trend is to have a low HTHS number to get better fuel economy at the risk of bearing journals. Long haul fleet managers still like a high number though.

Raso Tech - HTHS (High-Temperature, High-Shear) Explanation

 

[ovrszd]

Well, after reading a bunch on the subject of oil viscosity, I found out there is another number that is more important than just the weight of the oil.

"High Temperature High Shear HTHS viscosity measures the viscosity of an engine lubricant at 150°C and simulates the narrow tolerances and high speeds between moving parts in a hot engine. In particular bearings, the camshaft, the piston rings and liner."

So, normally, a 15w40 oil will have a higher HTHS number (~3.7) than the lower weights. Basically, the higher the number, the more heavy duty the oil is. You can get lower viscosity oil with a good HTHS but you pay for it.

Lately, the trend is to have a low HTHS number to get better fuel economy at the risk of bearing journals. Long haul fleet managers still like a high number though.

Raso Tech - HTHS (High-Temperature, High-Shear) Explanation

And my 22 year old 7.3L PS has drank 15w-40 all it's life. 270,000 miles worth. So I'll just continue with that.

 

[rScotty]

Based on what was available at the time of the equipment manufacture. 40 weight is 40 weight, so the lubricant properties of the oils are the same for warm weather. It’s just the winter performance that differs. I agree: why make 15w-40 oil anymore?

The answer to that is a bit of history combined with the way that multiweight oil is made. Multiweight oils are multiweight because of a deliberate change to the oil molecule. The change is an oil molecule that can wind and unwind so that it has has different viscosity at different temperatures. Unfortunately, doing that also changes the lubricity of the oil. And so as the viscosity range improved, the lubricity at different temperatures became a problem.
So for decades you didn't want a multiweight oil to have a very wide high viscosity range.

That is why early multi-weight oils were things like 20W-20 or 20W-30. Narrow viscosity range = better lubricity over the range. Remember back then??

For oil refiners the challenge was to create a multiweight oil with a wider range but still with acceptable lubricity across the temperature range.

And so it was quite a breakthrough when Rotella came up with a 15W-40 that had both a wide range of viscosity as well as retaining decent lubricity.

Now the range has been farther extended with commercial oils .... to 5W-40. Some of that extension is oil science and some of that is engine metallurgy, and some of that is definining just exactly what "lubricity" means.

That doesn't mean that the 5W-40 is simply 15W-40 with a wider range. If your use and/or climate is such that you don't do a lot of cold weather starts (cold weather starts = high wear) then frankly I'd stick with 15W-40. For that matter, if I lived in Florida or always always kept my diesel in a warm shop then I'd go with 20W-40.
Hope that helps,
rScotty

 

[California]

Multiweight oils are multiweight because of a deliberate change to the oil molecule. The change is an oil molecule that can wind and unwind so that it has has different viscosity at different temperatures. Unfortunately, doing that also changes the lubricity of the oil....
So for decades you didn't want a multiweight oil to have a very wide high viscosity range.

Scotty, maybe you have some insight to an issue discussed in the Yanmar forum: the concern that modern 15w40 is thicker and not as good for the classic Yanmars, compared to the originally specified 30 wt. Any comments?

 

[rScotty]

Scotty, maybe you have some insight to an issue discussed in the Yanmar forum: the concern that modern 15w40 is thicker and not as good for the classic Yanmars, compared to the originally specified 30 wt. Any comments?

Hello California, how is the apple crop this year?
Fruits of all kinds were bumper this year in Colorado. Wet spring, average summer, dry warm fall...

On oils, good question. I think about it a lot and so far have to say in 60+ years I've never seen an engine failure that I could say without a doubt was due to type of the oil...and that includes some real oddball oils.
There have been some grease joint failures.... that I'm just positive were due to the grease chemistry. And I've suspected lubricity failure in some common sump transmission+hydraulics.
But never an engine failure.

Maybe I just missed seeing it. But engine oil seems to be very good. I wish the rest of the lubricant world would catch up.

IMHO, today's 15W40 oil beats the pants off the old fashioned straight weight engine in a lot of ways - but we didn't have trouble with that old straight weight oil either.
rScotty

 

[Hay Dude]

And my 22 year old 7.3L PS has drank 15w-40 all it's life. 270,000 miles worth. So I'll just continue with that.

The good thing about them is they made low power for all their displacement. Might help em live longer?

 

[jyoutz]

The answer to that is a bit of history combined with the way that multiweight oil is made. Multiweight oils are multiweight because of a deliberate change to the oil molecule. The change is an oil molecule that can wind and unwind so that it has has different viscosity at different temperatures. Unfortunately, doing that also changes the lubricity of the oil. And so as the viscosity range improved, the lubricity at different temperatures became a problem.
So for decades you didn't want a multiweight oil to have a very wide high viscosity range.

That is why early multi-weight oils were things like 20W-20 or 20W-30. Narrow viscosity range = better lubricity over the range. Remember back then??

For oil refiners the challenge was to create a multiweight oil with a wider range but still with acceptable lubricity across the temperature range.

And so it was quite a breakthrough when Rotella came up with a 15W-40 that had both a wide range of viscosity as well as retaining decent lubricity.

Now the range has been farther extended with commercial oils .... to 5W-40. Some of that extension is oil science and some of that is engine metallurgy, and some of that is definining just exactly what "lubricity" means.

That doesn't mean that the 5W-40 is simply 15W-40 with a wider range. If your use and/or climate is such that you don't do a lot of cold weather starts (cold weather starts = high wear) then frankly I'd stick with 15W-40. For that matter, if I lived in Florida or always always kept my diesel in a warm shop then I'd go with 20W-40.
Hope that helps,
rScotty

Very informative. Thanks

 

[jyoutz]

Must not be worked very hard. The good thing about them is they made low power for all their displacement.

Those old Ford 7.3 and Cummins diesels are famous for going 500k+ miles without a rebuild. I know of a local feed store owner who has a Dodge Cummins with over one million miles without a rebuild. It has only been used to pull trailers with hay and feed.

 

[California]

Hello California, how is the apple crop this year?
Fruits of all kinds were bumper this year in Colorado. Wet spring, average summer, dry warm fall...

IMHO, today's 15W40 oil beats the pants off the old fashioned straight weight engine in a lot of ways - but we didn't have trouble with that old straight weight oil either.
rScotty

Thanks for the comments on motor oils.

The drought here (an hour north of San Francisco) was terrible for the apple harvest. A normal year is 70 tons or better, occasionally less. Up to 120 tons a couple of times in my 20 years owning the place. Grandpa's old records once showed a year of 140 tons, before the more recent semi-dwarf replacement trees that are easier to harvest.

This year the lack of rain cut the apple crop down to nothing, 18 tons! The apples were sparse and the size of tennis balls, or smaller. The crew, same people every year, refused piecework (per bin) and chose hourly at minimum wage.

The contractor who prunes, tills, harvests my orchard along with several others said apples were dismal everywhere. On the other hand he had converted from apples to vineyard on his home parcel 25 years ago and said this was an excellent year for grapes. He fulfilled the maximum in his his contracts then had to truck grapes all over to move his entire crop. I think his drip irrigation in the vineyard made a normal year for him while my dry farming tracked the rainfall record. Strange times. Sounds like you got the nice seasons we wished we had.

I'm sorry to read about the massive fires there this week.

 

[Hay Dude]

Those old Ford 7.3 and Cummins diesels are famous for going 500k+ miles without a rebuild. I know of a local feed store owner who has a Dodge Cummins with over one million miles without a rebuild. It has only been used to pull trailers with hay and feed.

Yep.
Keep em down to 200-250hp and they can go a long time.
Cant pull much, but they last.
Cummins will last the longest. Just look at the block, crank and con rods on them. Only one of them that was true medium duty