SUDT

[Spiffy]

Skypup, I looked at that chart, and am also confused on the point it makes:

Is it saying that, starting at WW degrees, it takes XX minutes of running to get to a point where the fluid flows freely through a ZZ sized orifice at YY rate?

Or I could see where a very low powered continous torque motor could drive the fluid in a chart like that.

Generally, after you run a load long enough, the oil gets hot enough to lose viscosity and shear and you lose volumetric effieciency in pumps & motors (or a hydro tranny), but that graph would look the opposite.

/forums/images/graemlins/confused.gif

 

[SkyPup]

Multi grade SUDT flows so much better than single grade UDT at ALL Operational Temperatures it isn't funny , they only converge at the end of the graph @ 200*F......very rarely will anyones hydraulic oil reach over 180*F even in the most extreme circumstances. /forums/images/graemlins/shocked.gif

 

[bugstruck]

edit "I can't think of a situation where a multi-viscosity lubricant (i.e. SUDT) would *not* out-perform single-viscosity (UDT)"
After reading my post realized I should have quoted you and I also read down to Skypup's last post, where he noted the equal temps/equal flows. end edit

I can think of a situtation but it doesn't apply to normal tractor oil temps. It would perform equally at the top of that chart if your oil started at that temp. It doesn't. Skypup gave a me and others a real education on this several months ago and others well before that. I tested him hard, real hard, so no need for me to retrace that. I promised in that thread I'd one day comment on the UDT I put in my L3130 this winter. Had SUDT through 43 hours. Here it is in real world application, as I see it, on the performance end only. Other factors besides performance favor SUDT though.
1. UDT is slightly noisier on cold starts but you don't really notice that up above say 50F. On 25F starts it's definitely noticable and you get the sense you really need a long warm up.
2. The contols seem comparable down to about 40F, but the performance tails off pretty fast and hard below 30F. Everyting slows. However, at 65F and up I don't see any difference at all with a one minute warm up and straight to work.

Keep in mind that even on a 20F start the operator isn't going to notice much difference after the tractor is running 30 minutes and the oil heats. Now if I jump on the backhoe at 30 minutes it will be sluggish for the first cycle or two of a given cylinder, but not noticable after that.

I know this operator experience doesn't directly correlate to the flows Skypup posts, but it actually does say that flow changes at various temperatures, beyond being scientifically measurable, are operator observable.

Finally, I think if you can feel it, more is going on. Mine will be prematurely changed to one of the Premium oils before the next scheduled service. No rush, but it will happen.

I didn't notice that much difference the first night or two of colder temps as I did later after those lower temps were sustained.

 

[bugstruck]

"Generally, after you run a load long enough, the oil gets hot enough to lose viscosity and shear and you lose volumetric effieciency in pumps & motors (or a hydro tranny), but that graph would look the opposite."

Yes it would seem so. However, the multi viscosity oils are gaining viscosity as the temps increase up to some point. That would mean as temps increase the volumetric efficiency may not be impacted as one would assume. The single viscosity oil is lowering in viscosity up the entire temp path above the measure point. I used to know that viscosity measure point (baseline) temp but I forget it. Maybe someone will enlighten me, again.

 

[Berniep]

<font color="blue"> Judging from the fact one user in this thread noticed subpar performance with Deere, I have to wonder if the SUDT isn't a higher viscosity than Deere or the mechanic took the Deere oil from the wrong barrel. </font>

I bought a sealed 5 gallon container.

 

[Spiffy]

Sealed container, must have been right. From their specs I thought Deere oil would be closer to a multi than a single viscosity, but not knowing Kubota's specs it is hard to compare. Can't argue empirical evidence though; it works better for you: no brainer!

I'm still convinced that cross referencing won't hurt a system, but performance requires spec for spec for spec (which can mean a cross ref to be better or worse than orignal). /forums/images/graemlins/crazy.gif

 

[Spiffy]

You're right SSLs and PT's will run 160F easy enough but shouldn't top 180F; heating up an entire casting and having mechanical PTOs (instead of hydro) I doubt "traditional" tractors often cross 140F.

No coincidence on the covergence; a multi is supposed to perform at the low viscosity cold and the high viscosity warm, so it does make sense converging at 100C (the warm spec). But I'm still not quite sure how to read the graph you posted. Is the beginning 40C and the end 100C? Over a low temp range you can spec the viscosity of a single to match the application, else with the lower change in viscosity the multi will, no doubt, win (at least on viscosity; shear and other effects come into play, but a specialty oil like SUDT would have that engineered in too).